Amiga MA Magazine 1998 #6

home *** CD-ROM | disk | FTP | other *** search

/ Amiga MA Magazine 1998 #6 / amigamamagazinepolishissue1998.iso / coders / jËzyki_programowania / logo / powerlogo / users-guide.text < prev next >

Wrap

Text File | 1992-11-10 | 80KB | 2,331 lines

Power LOGO Release 1.3 Copyright 1992 by Gary Teachout This program is freeware, and may be distributed freely. It may be distributed along with other freely distributable software. All other rights reserved. It may not be sold for profit, or included as part of a commercial product without my permission. Power LOGO should be distributed together with the entire contents of the 'PowerLOGO' directory. No donations are required but they are accepted and appreciated. THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO ITS FITNESS FOR ANY PARTICULAR PURPOSE. This software is experimental and IT HAS DEFECTS, if you do not accept all of the risks and responsibilities of using defective software, then DO NOT USE THIS. Table of Contents Preface Acknowledgments Chapter 1 Power LOGO Features The Power LOGO dialect Chapter 2 Getting started Running LOGO Startup file Command window Project Files Chapter 3 Programming Words and Lists Instructions Procedures Recursion Chapter 4 Advanced Topics Files Graphics Turtles Sound Demons Messages and Ports System Memory User Memory Chapter 5 Primitives Appendix A Errors Appendix B Limits Appendix C Compatibility Appendix D Recommended Reading Preface Programming languages have evolved, and improved a great deal. Modern versions of BASIC, for example, bare little resemblance to those available ten years ago. Numbered lines are gone, subprograms have been added, and they now include support for modern hardware and user interfaces. Most of this progress has left LOGO behind. Because of its early success with elementary students, it has acquired a reputation as a toy language for kiddies. Most versions of LOGO have no modern improvements, like support for modern hardware or user interfaces. As a dialect of LISP, LOGO is actually a very powerful and versatile programming language. Power LOGO is an atempt to bring LOGO up to date, by adding the kind of features you would expect from any modern language. My priorities for Power LOGO are simplicity, and versatility, before compatibility. This file covers the details of Power LOGO, but it is not intended to teach the LOGO programming language. For learning LOGO I recommend Computer Science Logo Style, Volume 1, by Brian Harvey (see appendix D Recommended Reading). You can help me to improve this version of LOGO. Please contact me with any comments or bug reports. I am also interested in how you use LOGO, and would like to see your program examples, demos, tutorials, etc. Gary Teachout 10532 66 Place, W Mukilteo, WA 98275 USA Acknowledgments I would like to thank the following for helping to make PowerLOGO work as well as it does, and for saving me a lot of work: * Justin V. McCormick, for the PathMaster file selector (filerequest). * Software Dissidents, for the ILBM.Library (loadimage, saveimage). Chapter 1 Power LOGO Power LOGO is an experimental dialect of the LOGO programming language. It is a very high level language, easy to use, and easy to learn. Yet it has some low level power as well. Features * Power LOGO uses the simplest subset of LOGO syntax, and is defined by the simplest rules. * User defined procedures are not limited to a fixed number of inputs, they may be defined with required inputs, optional inputs, and local variables. * Much of the Amiga graphics capability is supported. Primitives are provided to open custom Intuition screens and windows, draw lines, patterned lines, text, flood fills, copy regions, etc. * Turtle graphics with multiple turtles. Each turtle may have its own sense of distance, direction, home, line pattern, etc. * A universal host message port for inter process communication, including ARexx support. * Demons (high-level interrupts) may be programmed to respond to events from the keyboard, menus, left mouse button, host message port, reply message port, and window close gadgets. * Menus may be attached to any window. Along with menu demons this allows LOGO programs to have friendly user interfaces. You may customize the LOGO user interface by attaching your own menus to the LOGO command window. * All arithmetic uses the Amiga 'mathieeedoubbas.library', this includes automatic support for 68881. * Sounds may be played on all four of the Amiga audio channels. * Power LOGO provides many primitives not typically found in LOGO. Primitives for arithmetic (frac, log, power...), flow of control (cond, dowhile, whenmenu, while...), words and lists (alphap, items, restof...), and more. The Power LOGO dialect Power LOGO differs from traditional LOGO in these important ways: * It is case sensitive. All primitives and keywords are lower case, all names and data defined may be any case. * Spaces are sacred. All LOGO objects (words, lists, list brackets, and parenthesis) must be separated by white space (a space, or a linefeed). * It uses prefix (polish) notation only. Inputs to a procedure follow to the right of the procedure name. There are no infix operations, no implied spaces, and no special delimiters. * It has no 'TO' or 'END' primitive. User defined procedures are just variables that contain a special type of list, and are defined using the 'make' primitive. This idea of programs as data is unusual but can be very useful. * There is no built-in text editor. Project files may be created and edited almost any text editor. * Other differences relate to the name, spelling, inputs, and behavior of individual primitives. While some of the above may seem restricting, it keeps Power LOGO simple, and should not be difficult to learn. Chapter 2 Getting started Running LOGO LOGO may be run in the usual way from the WorkBench or the CLI. You may exit LOGO by entering the quit command. Power LOGO should run on most Amiga computers, it requires about 250 K bytes, but can use all available memory if needed. To use the 'saveimage', and 'loadimage' commands, your LIBS: directory must contain the 'ILBM.Library' by Software Dissidents. Your LIBS: directory must also contain the Amiga 'mathieeedoubbas.library'. Startup file If a file called LOGO-Startup is found in the same directory with LOGO it will be loaded to initialize LOGO. This file should contain LOGO code that will load any project files in the 'argslist'. It may also be used to configure LOGO the way you like, and to load your own frequently used procedures, and data. The default 'LOGO-Startup' file will define some useful procedures, install a menu user interface, and load any project files selected, or named as arguments. Command window LOGO opens a window on the workbench screen as its command input and output window. You may enter and edit LOGO commands with these special keys. Backspace Delete character to the left of the cursor. Cursor Right Move cursor right one space. Cursor Left Move cursor left one space. Cursor Up Move backward through the command history. Cursor Down Move forward through the command history. Control-G Stop program, return to top level. Control-K Delete from cursor to end of line. Control-U Delete from cursor to start of line. Control-X Delete the line. Delete Delete character under the cursor. Return Enter list or instructions. Shift Cursor Right Move cursor to end of line. Shift Cursor Left Move cursor to start of line. The '? ' prompt means LOGO is waiting for a command. If the command line contains an open list (an open bracket '[' without a closing bracket ']') you will see the '1 > ' prompt allowing you to continue the list on another line. ? repeat 20 [ 1 > setcursor list random 40 random 20 1 > pr "HELLO! ] Project Files There is no built-in text editor. LOGO stores programs as ASCII text files, which may be created and modified using any text editor. Some text editors remove trailing blank spaces from the ends of lines, if this removes a space following a backslash it will cause problems. The 'save' primitive will save the contents of variables in the LOGO workspace, as 'make' commands. The 'load' primitive will execute the instructions in a file just as if typed into the command window. 'load', and 'save' complement one another. Comments may be included in project files by prefixing them with a semicolon (;), the semicolon and everything from it to the end of the line will be ignored (note that the semicolon must be surrounded by white space to be recognized as a comment character). Chapter 3 Programming Words and Lists In the Power LOGO programming environment, everything is either a word or a list. Words can be any sequence of characters. Words are separated from each other by blank spaces, to include a space (or a backslash) in a word it must be preceded by a backslash (\). Numbers are just a special type of word. Numbers prefixed with an '@' symbol will be recognized by some procedures as pointers. Lists can be any sequence of objects, which may be ether words or lists. Lists are identified by enclosing them in brackets '[]'. This-is-a-word! [ This is a list! ] Instructions Words and lists may be either data or instructions. An instruction is a procedure name followed by any inputs the procedure may require. When LOGO tries to evaluate a word it may treat it in one of three ways, as a literal, as a variable, or as a procedure. Words preceded by a quote (") character (called quoted words) are literal and evaluate as the word itself. For words that happen to be numbers or pointers the quote is not needed. Words preceded by a colon (:) character (called dotted words) refer to the contents (binding) of a variable name. A word by itself (no dots or quote) is evaluated as a procedure (unless it is a number or pointer). ? print 123 123 Here 'print' is a procedure, and the number '123' is its input. The 'print' procedure simply prints its inputs on next line in the command window. ? print [ This is a list! ] This is a list! In this example the list (everything between the brackets) is the input to the 'print' command. ? print "This-is-a-word! This-is-a-word! In this example the quote (") identifies the input as a literal word. The inputs to a procedure need not be literal, they may be the contents of a variable, or the output of another instruction. Instructions may be nested as inputs within other instructions. ? pr * 7 6 42 Here '*' is another procedure '6' and '7' are its inputs. '*' outputs the product of its inputs to pr ('pr' is just an abbreviation for 'print') which prints it on the next line. It is important to note that the sub-instruction '* 7 6' is not the input to 'pr', but is evaluated, and its output is the input to 'pr'. ? make "x 100 ? pr :x 100 In the first line the 'make' procedure assigns 100 as the contents of the variable 'x'. In the second line ':x' refers to the contents of 'x'. Each procedure has some number of required inputs (zero or more), and some number of optional inputs (zero or more). To include optional inputs the entire instruction must be enclosed in parenthesis. If only the required inputs are used, the parenthesis are not needed. Print requires one input but may have many. ? ( pr "PI "= 3.1415 ) PI = 3.1415 In this instruction 'pr' has three inputs. ? ( pr [ And the answer is ] * 4 ( + 1 2 3 ) ) And the answer is 24 This entire line is one instruction where 'pr' has two inputs, the first is the list '[ And the answer is ]', the second is the instruction '* 4 ( + 1 2 3 )'. This second instruction '*' has two inputs '4' and another instruction '( + 1 2 3 )'. Procedures Primitives are the procedures that are built-in to LOGO. You may define your own procedures and add them to LOGO. In Power LOGO a procedure is just a variable that contains a special type of list, and may be defined using the 'make' primitive. The first item in a procedure definition list is the word procedure. The second item is a list of lists of names of the inputs and local variables used by the procedure (the names list). The rest of the items in the definition are the instructions executed by the procedure. ? make "hello [ procedure [ ] pr [ Hello World ! ] ] ? hello Hello World ! Because this example procedure uses no inputs or local variables the names list may be empty. The first item of the variable names list is a list of required inputs. The second item is a list of optional inputs or a name to receive a list of optional inputs. The third item is a list of names of local variables. Local variables and unused optional inputs contain the empty list at the start. ? make "hello [ 1 > procedure [ [ ] [ :n ] ] 1 > repeat if numberp :n [ :n ] [ 1 ] [ 2 > pr [ Hello World ! ] ] ] ? hello Hello World ! ? ( hello 3 ) Hello World ! Hello World ! Hello World ! ? ( hello 0 ) This example uses one optional input. See the example files for other forms of names lists. Global, free, and local variables all work as they would in lisp. All variable names in a procedure names list are local within each call to that procedure. They are free variables to all procedures called from within that procedure or at a lower level. Recursion A procedure that includes a call to itself is called a recursive procedure. ? make "factorial [ 1 > procedure [ [ :f ] ] 1 > output if < 1 :f [ * :f factorial - :f 1 ] [ :f ] ] ? factorial 5 120 This procedure uses recursion to compute the factorial of its input. A procedure in which the recursive call is the last instruction is called tail recursive. Tail recursion is handled differently by LOGO because the local variables need not be preserved. Two cases are recognized as tail recursion, a recursive operation as the input to an 'output' command, or a recursive command followed by a 'stop' command. ? make "count100 [ 1 > procedure [ [ :x ] ] 1 > pr :x 1 > if < :x 100 [ output count100 + :x 1 ] [ output :x ] ] ? make "count-up [ 1 > procedure [ [ :x ] ] 1 > pr :x 1 > count-up + :x 1 1 > stop ] In the second example the 'stop' command is never executed, but it is necessary for LOGO to recognize the call to 'count-up' as tail recursion, without it 'count-x' would run out of memory. Chapter 4 Advanced Topics Files Primitives are provided to save and load the contents of variables (including procedures), read and write data, save and load IFF images, attach icons to files, and get a filename through a file requester. The 'save' primitive saves the contents of variables to a file as 'make' commands. The 'load' command executes a text file as if it were typed at the command window except that comments are ignored (a comment is everything from a semicolon ';' to the end of the line). The 'saveimage', and 'loadimage' primitives copy the contents of a window to or from an IFF ILBM file. For these to work the 'ILBM.Library' by Software Dissidents must be in the LIBS: directory. The 'filerequest' primitive outputs an AmigaDOS file name selected with the PathMaster file selector by Justin V. McCormick. 'filerequest' may be used as input to any procedure that requires a file name. make "file-name filerequest load :file-name To read or write a data file it must first be opened with 'open' (a new file to be written), or 'openold' (an existing file to be read or appended). Each of these outputs a file pointer (a BCPL pointer to an AmigaDOS file handle) which must later be closed using 'close'. The primitives for reading and writing files accept a file-pointer as input and work much like their command window counterparts. This example will create or overwrite a file: make "file-handle open filerequest fprint :file-handle [ The quick brown fox... ] close :file-handle This example will read an existing text file into a list of lists: make "text-list [ ] make "file-handle openold filerequest while [ make "line freadlist :file-handle not wordp :line ] [ make "text-list lput :line :text-list ] close :file-handle Graphics Much of the Amiga graphics capability is available in Power LOGO. Primitives are provided to open custom intuition screens and windows, draw lines, patterned lines, text, flood fills, and copy regions. Graphics are rendered into windows which must first be opened with 'openwindow'. make "myscreen ( openscreen 3 2 [ My Screen ] ) make "mywindow ( openwindow :myscreen 3 [ My Window ] 50 30 500 150 ) The window graphics primitives require a pointer to a window as an input. Coordinates within windows start with (0,0) in the upper left corner and count pixels to the right and down. setpen :mywindow 1 move :mywindow 20 20 draw :mywindow 400 80 text :mywindow [ Window Graphics ] closescreen :myscreen Windows may be closed using 'closewindow', 'closescreen' will also close any windows that were open on that screen. Turtles Turtles are graphics tools based on relative movement. You may open many turtles, each is opened onto a window, has its own coordinate system, and has its own sense of location, distance, and direction, as well as its own foreground pen, background pen, draw mode, and line pattern. Turtles must be opened onto a window with 'openturtle' (the 'Turtle-Shell' file will do this for you). make "myscreen ( openscreen 3 2 [ My Screen ] ) make "mywindow openwindow :myscreen make "myturtle openturtle :mywindow By default the turtle commands control all active turtles, but may be directed to control specific turtles (active or not). repeat 32 [ fd 50 rt 170 ] Turtle operations output information about one specified turtle. make "pos tpos :myturtle make "head heading :myturtle Turtles may be closed with 'closeturtle', but 'closewindow, and 'closescreen' will also close any turtles that were open on that window or screen. Sound Sounds may be played on all four of the Amiga audio channels. Audio waveform data is an array of one byte signed numbers (-127 to 127) and must first be placed into chip ram. This will create a simple sound: make "sound-data allocchip 16 make "i 0 make "x 120 repeat 16 [ poke 1 psum :sound-data :i :x make "i + :i 1 make "x - :x 16 ] sound ( se :sound-data 16 250 64 100 ) [ ] [ ] [ ] sound ( se :sound-data 16 240 64 100 ) [ ] [ ] [ ] sound ( se :sound-data 16 300 64 100 ) [ ] [ ] [ ] The 'sound' command may then be played repeatedly. Demons A demon may be thought of as a process separate from your main program, that keeps testing for a particular kind of event. When the event is detected the demon interrupts the main program and runs a special procedure. When the procedure is complete the main program will resume. There are six types of events that may trigger demons, menu selection, left mouse button, key stroke, window close gadget, host message port, and reply message port. For each of these there is an event queue, when the event queue is not empty, the demon procedure will be run. The demon procedure must execute the appropriate get operation to remove the event from the queue, or the demon will run again and again. make "m-window openwindow [ @0 131 [ Mouse Paint ] 320 ] whenmouse [ while [ mousep ] [ make "m-d getmouse ] ; Remove mouse event. if = :m-window first :m-d [ ; Correct window? move :m-window item 2 :m-d item 3 :m-d ; Move cursor. make "m-d mouse :m-window ; Check mouse. while [ = 1 item 3 :m-d ] [ ; While button is down draw :m-window first :m-d item 2 :m-d ; Draw to pointer. make "m-d mouse :m-window ; Check mouse. ] ] [ ] ] This simple example of demons in action is from the example file 'Mouse-Paint'. For more examples of demons see the 'LOGO-Startup', 'Turtle-Shell', and 'ARexx-Support' files. Messages and Ports A general purpose message port is available for inter process comunication. A message is just an area of memory, sending a message is just a way of telling another Amiga program that it can look at or change this message. When the other program is through with the message it should reply to it. After sending a message a program must not alter the message until the reply is received. To receive messages programs must have a message port. Ports are identified by name, the default name for LOGOs host port is 'LOGO' (it can be changed). If more than one copy of LOGO is running, they will have names 'LOGO 2', 'LOGO 3', etc. A message must be at least twenty bytes long, the first twenty bytes are used by the Amiga system to keep track of the message when sent. Run two copies of LOGO, and this example will send lines typed into one copy of LOGO, and print them on the other: In the first copy of LOGO: while [ true ] [ make "message getmessage pr convertstring ( peek 0 :message 5 ) replymessage :message ] In the second copy of LOGO: make "message allocmem 24 ( poke 2 :m-packet 24 9 ) while [ true ] [ type "message? ( poke 0 :message allocstring rl 5 ) sendmessage "LOGO :message make "x getreply freemem ( peek 0 :message 5 ) ] The 'host-port-demon' in the 'LOGO-Startup', and 'ARexx-Support' files allows other programs to send commands to LOGO. These files also include procedures for sending messages to ARexx, another copy of LOGO, or other programs. System Memory For its own internal use LOGO allocates memory in even 8K byte blocks, and divides these blocks into small pieces called nodes. When out of nodes, LOGO runs the garbage collector to search all allocated blocks, and recycle any nodes that are no longer in use. if the collector finds less than a certain amount of free memory, it will allocate more blocks. All of this is dynamic and automatic, and need not be considered when programming in LOGO. However it is sometimes useful to be able to control this process. How often the collector runs depends on the amount of extra memory it tries to hold in reserve. The operation: system 1 will output this amount in bytes. The command: ( system 2 bytes ) will set this amount (where 'bytes' is a number). When this number is large, the collector will run less often, but more slowly. When the garbage collector runs you may notice a brief pause. The command: ( recycle 1 ) will force a normal recycle, and may be used to reduce the chance of the collector causing a pause at a bad time. The command: recycle will also force a recycle, but will also deallocate most of the extra memory LOGO would normally hold in reserve. This may be used prior to 'openscreen', 'openwindow', or other memory hungry actions. Note that LOGO will soon reallocate most of this memory. User Memory Sometimes you may need an area of memory for a special purpose (see the Sound, and Messages sections above). The 'allocmem', 'allocchip', and 'allocstring' primitives each allocate a block of memory and output a pointer. make "block allocmem :size make "chip allocchip :size make "string allocstring [ The frog sat on the log. ] 'allocmem' and 'allocchip' output a pointer to a block of memory of the size specified. 'allocstring' outputs a pointer to a null-terminated string compatible with both C and ARexx. When you are through with it you may return the memory with 'freemem'. freemem :block freemem :chip freemem :string LOGO also keeps a list of all these blocks and will free them when you give the command 'new' or 'quit'. If you do not want LOGO to free a block automatically use 'false' as an optional input (this is used for reply strings to ARexx). make "string ( allocstring [ function reply ] false ) Or to free a block not in LOGOs user memory list (this is used for reply strings from ARexx). ( freemem :string false ) To help keep track LOGO allways allocates eight bytes more than needed, stores the total size in the first four bytes, and outputs a pointer to the ninth byte instead of the first. 'freemem' requires a pointer of this type. Chapter 5 Primitives Format for descriptions of primitives: NAME INPUTS ( OPTIONAL-INPUTS ) SYNONYM ALTERNATIVE INPUTS INPUT = DESCRIPTION OF INPUT. FUNCTION DESCRIPTION. The Power LOGO primitive set: + number number ( number... ) sum number = Any number. Addition, output the sum of all inputs. - number number ( number... ) difference number = Any number. Subtraction, output first input minus all of the other inputs. * number number ( number... ) product number = Any number. Multiplication, output product of all inputs. / number number ( number... ) quotient number = Any number. Division, output first input divided by each of the other inputs. +- number negate number = Any number. Change sign, output opposite of input. > number number ( number... ) number = Any number. Output true if first input is more than all others. < number number ( number... ) number = Any number. Output true if first input is less than all others. >= number number ( number... ) number = Any number. Output true if first input is more than or equal to all others. <= number number ( number... ) number = Any number. Output true if first input is less than or equal to all others. =0 number ( number... ) number = Any number. Output true if all inputs are equal to zero. <0 number ( number... ) number = Any number. Output true if all inputs are less than zero. >0 number ( number... ) number = Any number. Output true if all inputs are more than zero. >> number number number ( number ... ) number = Any number. Output true if the rest of the inputs are between the first two. >>= number number number ( number ... ) number = Any number. Output true if the rest of the inputs are between or equal to the first two. abs number number = Any number. Output absolute value of number. acos cosine cosine = Number between -1 and 1. Inverse cosine, output angle of cosine. activelist Output list of pointers to active turtles. allocchip bytes ( predicate ) bytes = Number of bytes. predicate = true or false. Allocate chip memory, output pointer, for sound waveform data, etc. This allocates eight bytes more than specified, stores the total size in the first long-word, and outputs a pointer to the eighth byte. If 'predicate' is 'true' (or absent) memory will be placed in the user memory list for LOGO to keep track of so it can be deallocated automatically. If 'predicate' is 'false' LOGO keeps no record of this memory. See Also: freemem allocmem bytes ( predicate ) bytes = Number of bytes. predicate = true or false. Allocate memory, output pointer, for messages, arrays, etc. This allocates eight bytes more than specified, stores the total size in the first long-word, and outputs a pointer to the eighth byte. If 'predicate' is 'true' (or absent) memory will be placed in the user memory list for LOGO to keep track of so it can be deallocated automatically. If 'predicate' is 'false' LOGO keeps no record of this memory. See Also: freemem allocstring object ( predicate ) object = Any word or list. predicate = true or false. Create an ARexx argstring out of object, output pointer. This allocates eight bytes more than is needed for the string, stores the total size in the first long-word, and outputs a pointer to the eighth byte (the first byte of the NULL terminated string). If 'predicate' is 'true' (or absent) memory will be placed in the user memory list for LOGO to keep track of so it can be deallocated automatically. If 'predicate' is 'false' LOGO keeps no record of this memory. See Also: freemem alphap word word word = Any word. Output true if words are in alphabetical order. and predicate predicate ( predicate... ) predicate = true or false. Output true if all inputs are true. argslist Output list of startup arguments, the first item in the argslist is the file name of LOGO, the rest are the args from Workbench, or CLI. ascii word word = Any word. Output ASCII number of first character in word. asin sine sine = Number between 1 and -1. Inverse sine, output angle of sine. atan tangent tangent = Any number. Inverse tangent, output angle for tangent. back distance ( turtle ... ) bk distance ( turtle-list ) distance = Number, distance in turtle steps. turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Move turtles backward distance. break Jump out of looping primitives ('repeat', 'while', and 'dowhile'). buriedp object object = Any word or list. Output true if input is a buried variable name. burylist Output list of names that are buried. bury name ( name... ) name-list ( name-list... ) name = Word, a variable name. name-list = List of names. Hide and protect input variable names (hide from make, erase, namelist, etc.). See Also: unbury butfirst object bf object = Any word or list. Output all but the first item of the input object. butlast object bl object = Any word or list. Output all but the last item of the input object. catch label run-list label = Any word. run-list = List of LOGO instructions. Execute run-list, set trap for matching throw. The label 'error' may be used to trap errors. See Also: throw cd ( path ) path = An AmigaDOS directory name (word or list). Set the current directory to the specified path, or output the current directory. char ascii ascii = Any number from 1 to 255. Output word containing one ASCII character. clean ( turtle ... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Blank turtles windows without otherwise affecting the turtles. cleartext Blank the command window and set the cursor position to the upper left corner. close file ( file... ) file = BCPL pointer to AmigaDOS file handle. Close files. See Also: open, openold closep Output true if window-close queue is not empty. See Also: getclose closepalette predicate predicate = true or false. Close the palette tool. If predicate is true, any color changes are kept (same as the close or 'OK' gadgets). If predicate is false, the colors are reset (same as the 'CANCEL' gadget). See Also: openpalette, palettep closescreen screen ( screen... ) screen = Pointer to an intuition screen. Close screens. See Also: openscreen closeturtle turtle ( turtle... ) turtle-list turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Close turtles. See Also: openturtle closewindow window ( window... ) window = Pointer to an intuition window. Close windows. See Also: openwindow conditional conditional-list cond conditional-list = A list: [ predicate-list run-list ... ] predicate-list = A run-list that outputs true or false. run-list = List of LOGO instructions. Execute the run-list following the first true predicate-list. continue Skip to next pass in looping primitives ('repeat', 'while', and 'dowhile'). convertstring string string = Pointer to an ARexx argstring, or any NULL terminated text string. Output list of contents from a string. Reads a list from a NULL terminated text string. See Also: allocstring copyrect window X Y window X Y width height ( minterm ) window = Pointer to an intuition window. X = Number, pixel x coordinate. Y = Number, pixel y coordinate. width = Number, width of region in pixels. height = Number, height of region in pixels. minterm = Number, 0 to 255: 192 plain copy (default) 80 ignore source invert destination 48 invert copy See the Amiga Hardware Refrence Manual for more about minterms. Copy a rectangular region from window to window. cos angle angle = Number representing an angle. Output cosine of angle. count object object = Any word or list. Output number of items in object. cursor Output position-list of command window text cursor. dec name name = Word, a variable name that contains a number. Decrement variable. Subtract one from the number contained by name. degrees Interpret angles as degrees. See Also: radians dir ( path ) path = An AmigaDOS directory name (word or list). Output list of contents of the specified path, or the current directory. doscommand command-line command-line = List containing an AmigaDOS command line. Run list as AmigaDOS command (as if typed at the CLI). dot ( turtle ... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Mark one pixel at turtles position. dowhile run-list predicate-list run-list = List of LOGO instructions. predicate-list = A run-list that outputs true or false. Execute run-list while predicate-list is true. See Also: break, continue downp turtle turtle = Pointer to a turtle. Output true if turtles pen is down. draw window X Y window = Pointer to an intuition window. X = Number, pixel x coordinate. Y = Number, pixel y coordinate. Draw from a windows graphics cursor position to position X Y. emptyp object object = Any word or list. Output true if object is the empty list or the empty word. eqp object object ( object... ) object = Any word or list. Output true if all inputs refer to the same object. This is a special purpous operation, and is of limited usefulness. See Also: repitem, represt equalp object object ( object... ) = object = Any word or list. Output true if objects are identical. erase name ( name... ) name-list ( name-list... ) name = Word, a variable name. name-list = List of names. Remove bindings (contents) of input names that are not buried. See Also: make error Output list containing the error number, procedure name, primitive name, and the offending input from the most recent error. exor predicate predicate predicate = true or false. Output true if one input is true and one is false. filelist Output list of pointers to all open files. filerequest ( title ) title = Word, title bar text. Output file path name selected from file requester (or empty word if `cancel' is selected). This uses the PathMaster file selector by Justin V. McCormick. findport port-name port-name = Word or list, name of public message port. Output pointer to the message port if it exists. Output null pointer (@0) if the port does not exist. first object object = Any word or list. Output first item of object. firstput object object fput object = Any word or list. Output object made by adding first input to beginning of second input. floodol window X Y window = Pointer to an intuition window. Y = Number, pixel x coordinate. Y = Number, pixel y coordinate. Flood fill to outline. Recolor in all directions from X, Y to a border in the outline pen. floodpc window X Y window = Pointer to an intuition window. Y = Number, pixel x coordinate. Y = Number, pixel y coordinate. Flood fill pixel color. Recolor in all directions from X, Y all adjacent pixels the same color as X, Y. forward distance ( turtle ... ) fd distance ( turtle-list ) distance = Number, distance in turtle steps. turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Move turtles forward distance. fprint file object ( object... ) file = BCPL pointer to AmigaDOS file handle. object = Any word or list. Print object to file, followed by a linefeed. If object is a list outermost brakets will be removed. See Also: freadlist fprintout file name ( name... ) file name-list ( name-list... ) file = BCPL pointer to AmigaDOS file handle. name = Word, a variable name. name-list = List of names. Print names and their bindings file. Prints a 'make' command that may then be 'load'ed. See Also: load, make frac number number = Any number. Output fractional portion of number. freadbyte file file = BCPL pointer to AmigaDOS file handle. Output one byte number read from file, Output the empty list if end of file. See Also: fwritebyte freadlist file file = BCPL pointer to AmigaDOS file handle. Output list read from file (or the empty word if end of file). See Also: fprint freemem pointer ( predicate ) pointer = Pointer to allocated memory. predicate = true or false. Deallocate memory allocated by 'allocchip', 'allocmem', or 'allocstring'. If 'predicate' is 'true' (or absent) memory will only be deallocated if it is found in the user memory list. If 'predicate' is 'false' memory will be deallocated even if not found in the user memory list. This may be used to deallocate an ARexx argstring result. See Also: allocchip, allocmem, allocstring fshow file object ( object... ) file = BCPL pointer to AmigaDOS file handle. object = Any word or list. Print object to file, followed by a linefeed. ftype file object ( object... ) file = BCPL pointer to AmigaDOS file handle. object = Any word or list. Print object to file, not followed by a linefeed. fwritebyte file number ( number... ) file = BCPL pointer to AmigaDOS file handle. number = Any number from 0 to 255. Write one byte numbers to file. See Also: freadbyte getclose Output a pointer to a window from the window close event queue, wait if the event queue is empty. See Also: closep, whenclose getmenu Output list containing a pointer to the window, the menu number, item number, and subitem number of the next item from the menu event queue, wait if the menu event queue is empty. See Also: menup, whenmenu getmessage Output pointer to next message at the host port, wait if its empty. See Also: messagep, whenmessage, replymessage getmouse Output list containing a pointer to the window, the X position, and Y position where the mouse was when the button was pressed, wait if the mouse event queue is empty. See Also: mousep, whenmouse getprop name property gprop name = Word, name of a variable containing a property list. property = Word, label of an object in a property list. Output specified object from a property list. If `name' does not exist, the empty list is returned. If `property' does not exist for that `name', the empty list is returned. See Also: putprop, remprop getreply Output pointer to next message at the reply port, wait if its empty. See Also: replyp, whenreply heading turtle turtle = Pointer to a turtle. Output a turtles heading. home ( turtle ... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Move turtles to position (0,0) set heading to 0. hostport ( port-name ) port-name = Word or list, name for host message port. Without an input, outputs the name of the host port. With an input, changes the name of the host port. if predicate run-list run-list predicate = true or false. run-list = List of LOGO instructions. If predicate is true execute first run-list, if false execute second run-list. Both run-lists are required, if one case is not used, use the empty list [ ]. inc name name = Word, a variable name that contains a number. Increment variable. Add one to the number contained by name. int number number = Any number. Output integer portion of number. intuition action pointer ( ?... ) action = A number from 1 to 11, specifying action to be taken. pointer = A pointer to an intuition screen or window. ? = Listed below. Fourteen primitives in one, to modify screens, windows, and menus. 1 screen X Y X = Number, pixel x coordinate. Y = Number, pixel y coordinate. Move screen (screen = @0 for workbench screen). 2 window X Y X = Number, pixel x coordinate. Y = Number, pixel y coordinate. Move window (window = @0 for command window). 3 window menu item subitem menu, item, subitem = Numbers specifying a menu or item. Off menu (window = @0 for command window). 4 window menu item subitem menu, item, subitem = Numbers specifying a menu or item. On menu (window = @0 for command window). 5 screen Screen to back (screen = @0 for workbench screen). 6 screen Screen to front (screen = @0 for workbench screen). 7 screen showit showit = Number. Show screen title (number <> 0) hide title (number = 0). 8 window width height width = Number, width of window in pixels. height = Number, height of window in pixels. Size window (window = @0 for command window). 9 window MinWidth MinHeight MaxWidth MaxHeight MinWidth \ MinHeight \ MaxWidth / = Numbers, sizes in pixels. MaxHeight / Set window limits (window = @0 for command window). 10 window Window to back (window = @0 for command window). 11 window Window to front (window = @0 for command window). 12 window Make window, the active window. 13 window menu item subitem menu, item, subitem = Numbers specifying a menu or item. Set menu checkmark. 14 window menu item subitem menu, item, subitem = Numbers specifying a menu or item. Clear menu checkmark. item element object element = Number, index to item. object = Any word or list. Output specified item from object. items first count object first = Number, index to first item. count = Number of items. object = Any word or list. Output specified items from object. keyp Output true if character queue is not empty. See Also: readchar, whenchar last object object = Any word or list. Output last item from object. lastput object object lput object = Any word or list. Output object made by adding first input to end of second input. launch run-list run-list = List of LOGO instructions. Add run-list to a queue to be executed once prior to returning to top level. left angle ( turtle ... ) lt angle ( turtle-list ) angle = Number representing an angle. turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Rotate turtle left. linep Output true if command window input line queue is not empty. See Also: readlist listp object object = Any word or list. Output true if object is a list. list object object ( object... ) object = Any word or list. Output list containing input objects. load file-name ( file-name... ) file-name = An AmigaDOS file name (word or list). Load file, runs a text file as if it were typed at the keyboard. See Also: fprintout, save loadimage window file-name window = Pointer to an intuition window. file-name = An AmigaDOS file name (word or list). Load a window from an IFF ILBM file. Requires 'ilbm.library' from Dissidents Software. BUG: sometimes loads entire screen. log base number base = Positive number. number = Positive number. Output logarithm of the number to the base. make name object name = Word, a variable name. object = Any word or list. Make object the contents of name (bind object to name). Make is the LOGO variable assignment operator. See Also: erase, bury memberp object object object = Any word or list. Output true if the second object contains the first object. If both objects are words, only the first character of the first object is considered. menup Output true if menu queue is not empty. See Also: getmenu, whenmenu messagep Output true if the host port is not empty. See Also: getmessage, whenmessage mousep Output true if mouse-button queue is not empty. See Also: getmouse, whenmouse mouse window window = Pointer to an intuition window. Output list containing the X position, Y position and button position of the mouse relative to the window. move window X Y window = Pointer to an intuition window. X = Number, pixel x coordinate. Y = Number, pixel y coordinate. Move a windows graphics cursor to position X Y. movecommand screen ( le te w h ) screen = Pointer to an intuition screen, @0 for workbench screen. le = Number, left edge. \ te = Number, top edge. \ _ Dimensions for command window. w = Number, width. / h = Number, height. / Move the LOGO command window to another screen. namelist Output list of variable names in use. namep object object = Any word or list. Outputs true if `object' is a word that is the name of an unburied variable. Outputs false if it is a list, buried name, procedure name, or non-existant name. new Remove bindings of all names (erase), close all files, close all turtles, close all windows, close all screens, clear all menus, clear all demons, flush all input queues (eccept message ports), return to top level. not predicate predicate = true or false. Output true if input is false output false if input is true. numberp object object = Any word or list. Output true if object is a number. open file-name file-name = An AmigaDOS file name (word or list). Create or open file to be written, output BCPL pointer to an AmigaDOS file handle. See Also: close, openold openold file-name file-name = An AmigaDOS file name (word or list). Open existing file to be read or written, output BCPL pointer to an AmigaDOS file handle. See Also: close, open openpalette predicate screen ( le te ) predicate = true or false. screen = Pointer to an intuition screen, @0 for workbench screen. le = Number, left edge. te = Number, top edge. Open the palette tool, output window pointer. If palette was allready open, it will first be closed based on predicate. Note that the palette is a window and can have menus. See Also: closepalette, palettep openscreen vm ( d t le te w h dp bp ) screen-data-list vm = Number, viewport modes, sum of: 1 hires 2 lace 4 extra half brite d = Number of bit planes. t = List, title bar text. le = Number, left edge. te = Number, top edge. w = Number, width. h = Number, height. dp = Number, detail pen. bp = Number, block pen. screen-data-list = List containing some or all of the above. Default screen-data-list = [ 0 2 [ ] 0 0 320 200 0 1 ] if view modes = hires then default width = 640 if view modes = lace then default height = 400 if view modes = extra half brite then default depth = 6 Open an intuition graphics screen, output pointer to the screen. See Also: closescreen openturtle window ( mag ar X Y h t ) turtle-data-list window = Pointer to an intuition window. mag = Number, scale or magnification. ar = Number, aspect ratio, pixel width / height. X = Number, pixel x coordinate of home. Y = Number, pixel y coordinate of home. h = Number, heading of home. t = Number, turning direction, >= 0 clockwise, < 0 counterclockwise (right and left are reversed). turtle-data-list = List containing some or all of the above. Defaults: mag lores 1.8 hires 3.2 This means it takes 200 steps to go from the left edge to the right edge of a full screen. ar lores 0.88 hires 0.44 lores lace 1.76 hires lace 0.88 This makes circles look round and squares look square. X, Y The current center of the window. h 0 Straight up. t 0 Clockwise. Open a turtle, output pointer to the turtle. See Also: closeturtle openwindow screen ( f t le te w h dp bp minw minh maxw maxh ) window-data-list screen = Pointer to an intuition screen, @0 for workbench screen. f = Number, flags, sum of: 1 drag gadget 2 depth gadget 4 close gadget 8 size gadget 16 give me zero zero 32 backdrop 64 borderless 128 activate t = List, title bar text. le = Number, left edge. te = Number, top edge. w = Number, width. h = Number, height. dp = Number, detail Pen. bp = Number, block Pen. minw = Number, minimum width. minh = Number, minimum height. maxw = Number, maximum width. maxh = Number, maximum height. window-data-list = List containing some or all of the above. Default window-data-list WorkBench screen: [ @0 3 [ ] 0 0 320 200 0 1 30 30 640 400 ] Default window for custom screen: Backdrop borderless window to fit the screen. Open an intuition graphics window, output pointer to the window. See Also: closewindow or predicate predicate ( predicate... ) predicate = true or false. Output true if any inputs are true. output object op object = Any word or list. Exit procedure, return object as the procedures output. palettep ( window ) window = Pointer to an intuition window (the palette tool ?). Test to see if window is the palette tool (is palette open ?), or wait for it to be closed, and or output how it was closed. See Also: openpalette, closepalette pd ( turtle ... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Pen down, lower the turtles pen. peek bytes address ( offset ) bytes = Number, one of: 0 32 bit pointer 1 8 bit unsigned integer -1 8 bit signed integer 2 16 bit unsigned integer -2 16 bit signed integer 4 32 bit unsigned integer -4 32 bit signed integer 8 64 bit IEEE double floating point number address = Number, or pointer, a memory address. offset = Number, offset in data items. Output number contained at memory address (address + (offset * (data size in bytes))). See Also: poke, psum pen window ( type ) window = Pointer to an intuition window (@0 for command window). type = Number, which pen: 0 foreground pen (default) 1 background pen 2 area outline pen Output the windows pen number. poerror Print out error message. pointerp object object = Any word or list. Output true if object is a pointer. poke bytes address number ( offset ) bytes = Number of bytes: 1 8 bit integer 2 16 bit integer 4 32 bit integer or pointer 8 64 bit IEEE double floating point number address = Number, or pointer, a memory address. number = Number, or pointer, limited in size by number of bytes. offset = Number, offset in data items. Deposit number at memory address (address + (offset * (data size in bytes))). Compatibility note as of release 1.3 'poke' no longer allows multiple numbers. See Also: peek, psum power base exponent base = Any number. exponent = Number, if base < 0 then exponent must be an integer. Output base to the power of exponent. precision ( digits ) digits = Number from 0 to 15. Sets or outputs precision used by print, fprint, type, ftype, and text when printing numbers. primitivep object object = Any word or list. Output true if object is a primitive. print object ( object... ) pr object = Any word or list. Print object to command window, followed by a carriage return, with outer brackets removed. printout name ( name... ) po name-list ( name-list... ) name = Word, a variable name. name-list = List of names. Print names and their bindings (i.e., the entire `make' command) to the command window. procedurep object object = Any word or list. Output true if object is a user defined procedure. psum address number ( number... ) address = Number, or pointer, a memory address. number = Any number. Output pointer equal to sum of address and numbers. See Also: peek, poke pu ( turtle... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Pen up, raise the turtles pen. putprop name property object pprop name = Word, name of a variable containing a property list. property = Word, label of an object in a property list. object = Any word or list. Place object into a property list. See Also: getprop, remprop quit Exit LOGO, return to WorkBench or CLI. LOGO cleans up after itself by closing all screens, windows, turtles, and files, and freeeing allocated memory in the user memory list. radians Interpret angles as radians. See Also: degrees rand Output random fraction from zero to less than one. random range range = Number, positive integer. Output random integer from zero to less than number. readchar rc Output one character word typed at keyboard. Reads characters from windows other than the command window. Waits if character event queue is empty. See Also: keyp, whenchar readlist rl Output line typed at keyboard as a list. Reads lines from the command window. Waits if line queue is empty. See Also: listp readpixel window X Y window = Pointer to an intuition window. X = Number, pixel x coordinate. Y = Number, pixel y coordinate. Output pen number of pixel at position (X,Y). rectfill window l t r b window = Pointer to an intuition window. l = Number, left edge of rectangle in pixels. t = Number, top edge of rectangle in pixels. r = Number, right edge of rectangle in pixels. b = Number, bottom edge of rectangle in pixels. Fill rectangle from (l,t) to (r,b). recycle ( number ) number = Any number. Without an input, recycles memory and frees what is normaly held in reserve. With an input, just recycles memory. remainder number number number = Any number. Output remainder after division. remprop name property name = Word, name of a variable containing a property list. property = Word, label of an object in a property list. Remove object from a property list. See Also: getprop, putprop repeat number run-list number = Number, positive integer. run-list = List of LOGO instructions. Execute run-list number of times. See Also: break, continue repitem item list object item = Number, index into list. list = Any list. object = Any word or list. Replace specified item of list with object. This special purpous command should NOT be used by any but the most experienced programmers. WARNING: repitem destructively changes an existing list and you may obtain unexpected results if there is more than one reference to the list. This is similar to 'rplaca' in Lisp. See Also: eqp, represt replymessage message message = Pointer to an Exec message. Return a message received at the host port. See Also: getmessage replyp Output true if the reply port is not empty. See Also: getreply, whenreply, sendmessage represt item list object item = Number, index into list. list = Any list. object = Any word or list. Replace rest of list after specified item with object. This special purpous command should NOT be used by any but the most experienced programmers. WARNING: represt destructively changes an existing list and you may obtain unexpected results if there is more than one reference to the list. This is similar to 'rplacd' in Lisp. See Also: eqp, repitem restof item object item = Number, index into object. object = Any word or list. Output rest of object following specified item. rgb screen index screen = Pointer to an intuition screen (@0 for workbench screen). index = Number, index into the screens color table. Output list containing red, green, and blue value of the screens specified color. right angle ( turtle ... ) rt angle ( turtle-list ) angle = Number representing an angle. turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Rotate turtle right. round number number = Any number. Output number rounded to nearest integer. run run-list run-list = List of LOGO instructions. Execute run-list. save file-name name ( name... ) file-name name-list ( name-list... ) file-name = An AmigaDOS file name (word or list). name = Word, a variable name. name-list = List of names. Save variable names and their contents to file with a project icon. See Also: load saveicon file-name ( default-tool tool-types ) file-name = An AmigaDOS file name ('.info' will be added). default-tool = Word. tool-types = List of up to three words. Attach icon to file. saveimage window file-name window = Pointer to an intuition window. file-name = An AmigaDOS file name (word or list). Save a window to an IFF ILBM file. Requires 'ilbm.library' from Dissidents Software. BUG: sometimes saves entire screen. screenlist Output list of pointers to all open screens. seconds Output system clock time in seconds. seedrand ( number ) number = Any number. Re-seed random number generator. seekend file file = BCPL pointer to AmigaDOS file handle. Move to end of file. seekstart file file = BCPL pointer to AmigaDOS file handle. Move to start of file. sendmessage port-name message ( predicate ) port-name = Word or list, name of public message port. message = Pointer to an Exec message. predicate = true or false. Send a message to the specified message port. 'predicate' indicates whether or not you want a reply. See Also: getreply, replyp sentence object object ( object... ) se object = Any word or list. Output list of input objects. Lists in the input to sentence will have their outer brackets removed. 'sentence' always creates a new list. setafpt window pattern-list window = Pointer to an intuition window. pattern-list = A list of up to 16 words, each 16 characters long where 'x' is an on pixel, any other character is an off pixel. Set area fill pattern. setcursor position position = List of two numbers, X, and Y coordinates. Set command window text cursor position. setdrmode window mode window = Pointer to an intuition window (@0 for command window). mode = Number, sum of: 0 JAM1 1 JAM2 2 COMPLEMENT 4 INVERSVID Set a windows draw mode. setfont window font-name font-height window = Pointer to an intuition window (@0 for command window). font-name = Word. font-height = Number. Set a windows text font. seth angle ( turtle ... ) angle ( turtle-list ) angle = Number representing an angle. turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Set turtles heading. setlinept window pattern window = Pointer to an intuition window. pattern = Word 16 characters long where 'x' is an on pixel, any other character is an off pixel. Set a windows line pattern. setmenu window menu-list ( front-pen back-pen ) window = Pointer to an intuition window (@0 for command window). menu-list = List of menu text: [ menu-name-1 [ item-1-1 K ] [ item-1-2 [ subitem-1-2-1 K ] [ subitem-1-2-2 K ] ] menu-name-2 [ item-2-1 ] [ item-2-2 ] ] (where 'K' is a keyboard short cut) front-pen = Number, pen for menu text. back-pen = Number, pen for menu background. Attach a menu strip to the window. setpen window pen ( type ) window = Pointer to an intuition window (@0 for command window). pen = Number of pen. type = Number, which pen: 0 foreground pen (default) 1 background pen 2 area outline pen Set a windows pen number. setrgb screen index rgb-list screen = Pointer to an intuition screen (@0 for workbench screen). index = Number, index into color registers table. rgb-list = List of three numbers, containing red, green, and blue value of the color. Set a screens color register. setstyle window style window = Pointer to an intuition window (@0 for command window). style = Number, sum of: 0 plain 1 underlined 2 bold 4 italic Set the text rendering style. settdm mode ( turtle ... ) mode ( turtle-list ) mode = Number, sum of: 0 JAM1 1 JAM2 2 COMPLEMENT 4 INVERSVID turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Set turtles draw mode. settlp pattern ( turtle ... ) pattern ( turtle-list ) pattern = Word 16 characters long where 'x' is an on pixel, any other character is an off pixel. turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Set turtle line pattern. settpn pen type ( turtle ... ) pen type ( turtle-list ) pen = Number of pen. type = Number, which pen: 0 foreground pen 1 background pen turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Set turtles pen number. settpos position ( turtle ... ) position ( turtle-list ) position = List of two numbers, X, and Y coordinates. turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Set turtles position. show object ( object... ) object = Any word or list. Print object to command window, followed by a carriage return, with outer brackets intact. sin angle angle = Number representing an angle. Output sine of angle. sleep Wait for an input event (mouse, menu, keyboard, window close, host port, or reply port). sound sound-list sound-list sound-list sound-list sound-list = list containing: sound data, pointer to an array of bytes (in chip ram). length, number of bytes of sound data. period, number, (microseconds per sample)/0.279. volume, number, loudness 0-64. cycles, number of times to repeat the sound. Play sounds and music on all four of the Amiga audio channels. Sound data must be prepared prior to use. sqrt number number = Positive number. Output square root of number. stick Output list containing the X position, Y position and button position of a joystick in port number two. stop Exit procedure. system action ( ? ) action = A number from 1 to 14, specifying action to be taken. ? = Listed below. Fourteen primitives in one, to control memory, libraries, and demons. 1 Output the amount of memory LOGO tries to hold in reserve. 2 bytes bytes = Number of bytes. Set the amount of memory LOGO tries to hold in reserve. 3 bytes bytes = Number of bytes. Allocate memory, this has been replaced by 'allocmem'. See Also: allocmem 4 bytes bytes = Number of bytes. Allocate chip memory, this has been replaced by 'allocchip'. See Also: allocchip 5 pointer pointer = Pointer to allocated memory. Free memory, this has been replaced by 'freemem'. See Also: allocchip, allocmem, allocstring, freemem 6 Output list of pointers to allocated memory blocks. See Also: allocchip, allocmem, allocstring, freemem 7 Open Diskfont library. 8 Close Diskfont library. 9 Open ILBM library. 10 Close ILBM library. 11 Enable demons. 12 Disable demons. 13 Open Icon library. 14 Close Icon library. 15 Output a real pointer to the command window. 16 Output a real pointer to the workbench screen. 17 Output launch list. 18 Output char demon list. 19 Output close demon list. 20 Output menu demon list. 21 Output mouse demon list. 22 Output host port demon list. 23 Output reply port demon list. tan angle angle = Number representing an angle. Output tangent of angle. tell turtle ( turtle... ) turtle-list turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Make these the active turtles, deactivate any other turtles. text window object window = Pointer to an intuition window. object = Any word or list. Print text to a custom window. thing name name = Word, a variable name. Output object bound to name (contents of variable). throw label label = Any word. Escape to catch with matching label. toplevel Stop all LOGO processing and return to the top level prompt. toward position turtle position = List of two numbers, X, and Y coordinates. turtle = Pointer to a turtle. Output heading to point turtle toward position. tpen turtle ( type ) turtle = Pointer to a turtle. type = Number, which pen: 0 foreground pen (default) 1 background pen Output the turtles pen number. tpos turtle turtle = Pointer to a turtle. Output a list containing the turtles position. turtlelist Output list of pointers to all open turtles. turtleoff ( turtle ... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Deactivate turtles. turtleon ( turtle ... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Activate turtles. twpos turtle turtle = Pointer to a turtle. Output Turtles position in window coordinates. type object ( object... ) object = Any word or list. Print the object (followed by a space) to the command window with outer brackets removed, and not followed by a carriage return. unbury name ( name... ) name-list ( name-list... ) name = Word, a variable name. name-list = List of names. Make variable names accessible. See Also: bury wait seconds seconds = Positive number. Pause for a number of seconds. whenchar run-list run-list = List of LOGO instructions. Set demon to run when key stroke is detected. Run-list must execute a 'readchar' to clear the character queue. See Also: keyp, readchar whenclose run-list run-list = List of LOGO instructions. Set demon to run when window-close is detected. Run-list must execute a 'getclose' to clear the window-close queue. See Also: closep, getclose whenmenu run-list run-list = List of LOGO instructions. Set demon to run when menu item is selected. Run-list must execute a 'getmenu' to clear the menu-selection queue. See Also: getmemu, menup whenmessage run-list Set demon to run when the host port is not empty. Run-list must execute a 'getmessage' to clear the host message port. See Also: getmessage, messagep, replymessage whenmouse run-list run-list = List of LOGO instructions. Set demon to run when mouse-button is pressed. Run-list must execute a 'getmouse' to clear the mouse-button queue. See Also: getmouse, mousep whenreply run-list Set demon to run when the reply port is not empty. Run-list must execute a 'getreply' to clear the reply port. See Also: getreply, replyp, sendmessage while predicate-list run-list predicate-list = A run-list that outputs true or false. run-list = List of LOGO instructions. While predicate-list is true, repeat run-list. See Also: break, continue window ( turtle ... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Allow turtle to move beyond edges of window. windowlist Output list of pointers to all open windows. word word word ( word... ) word = Any word. Output word made by concatenating the input words. wordp object object = Any word or list. Output true if object is a word. wrap ( turtle ... ) ( turtle-list ) turtle = Pointer to a turtle. turtle-list = List of turtle pointers. Make turtle wrap around at edges of window. writepixel window X Y window = Pointer to an intuition window. X = Number, pixel x coordinate. Y = Number, pixel y coordinate. Set pixel (X,Y) to the pen color. wtpos turtle turtle = Pointer to a turtle. Output windows position in turtle coordinates. Appendix A Errors Errors in syntax, or anything the interpreter does not recognize as valid LOGO instructions, should produce meaningful error messages. Primitives that expect a pointer as input may cause LOGO to crash (guru) if passed a bad pointer. The primitives 'repitem', and 'represt' destructively change an existing list and must be used carefully. If there is more than one reference to the list all references will be changed. They can also result in circular lists which appear infinite, and may cause LOGO to get stuck in a loop. Appendix B Limits * Lines typed at the command window are limited to 250 characters. * Lines in files being loaded are limited to 1000 characters. * Words may be no longer than 500 characters. * Primitives are limited to a maximum of 200 inputs. * Internally lists may be nested to any depth. But stack size will limit list depth for input and output. This is rare but if LOGO crashes while entering, printing, saving, loading, writing, or reading, a deeply nested list, try increasing the stack size. Appendix C Compatibility Though there is no official standard for LOGO, two dialects form the de facto standard: Those from LOGO Computer Systems Inc. (LCSI) (Apple LOGO II, Atari LOGO, Sprite LOGO), and what is called MIT LOGO (Krell, PC, Terrapin, Amiga). These are both good, and similar enough to both be called standard. With the following important exceptions Power LOGO follows the LCSI standard: Power LOGO is case sensitive. All primitives and keywords are lower case, all names and data defined may be any case. Spaces are sacred. All LOGO objects (words, lists, list brackets, and parenthesis) must be separated by a space, or a linefeed. Other dialects may accept lists like this: make "x [abc[12 3 45]ef g] In Power LOGO it would be: make "x [ abc [ 12 3 45 ] ef g ] Power LOGO uses prefix (polish) notation only. There are no infix operations, no implied spaces, no special delimiters, and no exceptions. Other dialects may accept arithmetic in this form: pr 5+2*7 In Power LOGO: pr + 5 * 2 7 Power LOGO has no 'TO' or 'END' primitive. User defined procedures are just variables that contain a special type of list, and are defined using the 'make' primitive. Here is a simple procedure that will work in most traditional dialects of LOGO: 1 TO HELLO 2 PR [ HELLO WORLD ] 3 END And a line by line translation into PowerLOGO: 1 make "hello [ procedure [ ] 2 pr [ Hello World ] 3 ] The word 'procedure' identifies this list as a procedure definition. Inputs and local variables are declared in a list following the word 'procedure' (the empty list indicates that this procedure has no inputs and no local variables). The names list is followed by the instructions that make up the procedure. The first item of the variable names list is a list of names of required inputs. The second item is a list of names of optional inputs. The third item is a list of names of local variables. TO COUNTUP :FROM :TO LOCAL :X MAKE "X 0 REPEAT :TO - :FROM [ PR :FROM + :X MAKE "X :X + 1 ] END In Power LOGO: make "countup [ procedure [ [ :from :to ] [ ] [ :x ] ] make "x 0 repeat - :to :from [ pr + :from :x make "x + :x 1 ] ] For most procedures the first line and the variable declarations will look very different. but the instructions that make up the body of the procedure will need little change. Other differences relate to the name, spelling, inputs, and behavior of individual primitives: In many dialects the 'if' primitive may have either two, or three inputs, the third input is the else action: if equalp :a :b [ pr true ] if equalp :a :b [ pr true ] [ pr false ] In Power LOGO the 'if' primitive always has three inputs. If the third input is not needed, use the empty list: if equalp :a :b [ pr true ] [ ] if equalp :a :b [ pr true ] [ pr false ] Turtle graphics commands should be compatible with most other dialects, but a window and a turtle must have been opened first (the startup, and turtles files will do this for you). Because of multiple turtles, operations that output data about a turtle must have a turtle-pointer as input. If you are using the provided turtle package, this will output the heading of the turtle: heading :tg-turtle Power LOGO has special primitives for reading and writing data files (open, close, fprint, freadlist, ect.). Appendix D Recommended Reading This document file describes the differences between Power LOGO and traditional versions of LOGO, these books will provide more background about LOGO. Two of these books, Computer Science Logo Style volume 1, and Visual Modeling with LOGO, include sections that may be helpful to beginners. Computer Science Logo Style Volume 1: Intermediate Programming, 1985. Volume 2: Projects, Styles, and Techniques, 1986. Volume 3: Advanced Topics, 1987. Brian Harvey MIT Press. These are excellent books for anyone interested in programming, and computer science. Mindstorms: Children, Computers, and Powerful Ideas. Seymour Papert Basic Books, 1980 This book is about education and how computers and programming may be used by children, parents, and teachers. Required reading for parents, and teachers interested in how children can make use of computers. Turtle Geometry: The Computer as a Medium for Exploring Mathematics. Harold Abelson, and Andrea diSessa MIT Press 1981 About turtles as a tool for the study of mathematics, geometry, and topology. Visual Modeling with LOGO: A Structural Approach to Seeing. James Clayson MIT Press, 1988 About using LOGO and turtle graphics for exploring visual ideas and relationships.