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USER'S GUIDE FOR KED A syntax-directed editor for KAREL the Robot A file is a conceptual device used to indicate a place where your program is stored. Creating or modifying a file is called editing the file. KED is a syntax-directed editor for the language used by KAREL the Robot [1] [2]. It allows you to create or modify syntactically correct programs for KAREL. This does not mean that your program is a correct solution to the problem you are trying to solve or that no "error shutoffs" will result; it means only that there are no lexical or syntactic errors in your program (see Sec. 2.6 in [1] for a detailed description of the various kinds of programming errors). You can use (or invoke) KED by typing: ked newfilename1 newfilename2 Use any legal filenames you wish. If this is a new program the names should be different from any in your directory. The first file is used by KED to keep track of the relationships in your program. The second file is used to hold the text of your program in case you should want to make a printed copy. If these are new files KED will respond with: TYPE MN TO SEE MENU BEGINNING-OF-PROGRAM <instruction> This indicates that the first line of your program has been typed in for you. The flashing underscore indicates where your typing will start and the word between brackets what sort of command is legal at this point. Now you can use KED to create your program. See Editing Session I which creates a new file. If you wish to edit an old file, simply use the same format: ked oldfilename1 oldfilename2 Here, the first file should be one created in an earlier session. KED will respond by getting your files and then printing out the first 20 lines of your program followed by a ? prompt. Now you can modify your program using the ---------- 1. Richard E. Pattis,KAREL the Robot A Gentle Introduction to the Art of Programming (New York: John Wiley & Sons, 1981) 2. All programs are written in C. insert and delete commands. If by mistake you give an old filename that does not contain a KAREL program you may exit gracefully by typing "q" and not saving the program. This will allow you to start over and not cause any damage to your old file. Constructs or control structures are used in a program to change the order of execution of instructions. In KAREL's language, the constructs begin with IF, WHILE or ITERATE. Inside the constructs there may be a single statement or several statements (a compound statement). If a compound statement is used, it is included between the reserved words BEGIN and END. If only a single statement is used, in order to make it clear to KED that the construct is completed, you must type the NDC (end of construct) command. An NDC is not needed to complete a construct containing a compound statement, since an END automatically causes KED to supply an NDC. An NDC would be required as indicated in the following program segment: ITERATE 6 TIMES turnleft; NDC (entered by user to complete ITERATE) IF front-is-blocked THEN turnoff NDC (entered by user to complete THEN) ELSE move; NDC (entered by user to complete ELSE) WHILE not-facing-north DO BEGIN move; turnleft END (no NDC is required to complete WHILE since a compound statement is used inside the construct) NDC does not add any statements to your program; it is only used by KED to structure relationships between constructs. For editing purposes, IF, THEN and ELSE are considered to be separate constructs. If any construct but ELSE follows THEN, KED will automatically perform the NDC so the instruction will follow the IF. IF facing-west THEN turnleft; NDC (entered by user to complete THEN) NDC (automatically performed by KED since the next entry is a not an ELSE) pickbeeper; This can cause some problems if there are several nested IF's. IF facing-west (5) THEN (4) IF facing-north (3) THEN (2) IF facing-south (1) THEN move; NDC NDC NDC NDC NDC move; In order to add the "move" after the outermost IF (the only legal location, since none of the statements is compound), NDC must be entered five times to end the indicated constructs. To add any of KAREL's instructions or tests to your program, simply type the one- to three-letter commands at the desired location and it will be automatically added. If you make a typing error, the backspace character won't correct the entry; simply let KED give you an INVALID COMMAND error message and re-enter the desired instruction. KED will attempt to guide you through this process with appropriate prompts for the kind of command to enter. Of course, you should always have written the complete program you wish to enter before you sit down at the terminal! After an instruction has been added, KED will prompt for the next legal entry: <instruction>, <test>, <new-name> or <positive-number>. Instructions are always automatically added to the end of the program. When you have added a DEFINE-NEW-INSTRUCTION, KED automatically adds a BEGIN and then will prompt for a new name; when you have added a WHILE or IF, KED will prompt for a test; when you have added an ITERATE, KED will prompt for a positive number. In any of these three situations, you must respond to the prompt; the only other alternative is to see the menu. Except for these situations, you can use any of the edit commands to examine your program at any time while adding instructions. Whenever you type MN, an updated menu will be printed at your terminal. User-defined instructions are added to the menu following the list of INSTRUCTIONS. After an instruction has been added, KED will respond with a prompt for the next kind of entry. After an edit command has been executed, KED will respond with a ?. No matter where you are examining your program, the next addition will always be at the end. The only way to add an instruction to the middle of your program is to type "i" to get in insert mode and that can only be done when your program has been completed (after END-OF-EXECUTION has been added). Suppose we had made the following errors when we entered the program in Editing Session I: 1. omitted one turnleft from the definition 2. typed turnleft instead of turnright following the THEN To correct these errors we can do the following (see Editing Session II): 1. go to the top of the program 2. go to the end of the definition 3. insert a turnleft before the END 4. go to the turnleft before the END of the THEN construct 5. delete the turnleft 6. insert a turnright The following conditions must be observed when inserting: 1. Insertions can only be performed when a complete program has been entered (after NDX has been added). 2. Insertions can only be made before END, DEFINE, BEGINNING- OF-EXECUTION, END-OF-EXECUTION or before a construct following BEGINNING-OF-EXECUTION that is not indented more than one level. This is actually a restriction on entering in the middle of a construct. 3. Once you are in "insert mode" you can continue adding instructions as you did when the original program was created. KED insures that a construct is always completed before the insert mode is exited. 4. To exit the "insert mode", simply type any edit command (except MN which will always print the menu but leave you in the insert mode). The following conditions must be observed when deleting: 1. You cannot delete: 1. BEGINNING-OF-PROGRAM 2. BEGINNING-OF-EXECUTION 3. END-OF-EXECUTION 2. You can only replace: 1. tests 2. new names 3. positive numbers 3. The replacement-only restriction for new names can be used to the programmer's advantage by using a shortened version of the actual name desired (e.g. ta instead of turn-around) to reduce typing in the instruction each time it is used in the program. After all the entering and testing has been completed, the user may then return to KED and substitute the longer version in the definition. This will automatically result in the new version's replacement of the old version throughout the program without any additional typing. 4. If you try to delete any capitalized word (reserved word), KED will ask if you wish to delete the entire construct. If you respond with a "Y", the entire construct will be removed from your program. If you delete a definition, all uses of the defined instruction will be removed from your program as well as the menu. Editing Session III will illustrate some of the more complicated insert and delete features of KED. To save the program, type "s". You cannot save an incomplete program, that is, NDX must always have been added. If you are editing an old file, at that time, the old file will be destroyed and the new version will be saved. If you do not wish to lose your old copy you must make a "back-up" and place it in your directory before you start the editing session. If you are creating a new file, a file will be placed in your directory containing your program. Remember, the first file contains the relationships and the second contains the text. To end the editing session, type q (quit). KED will remind you to save your program and then end after reading your answer. ERROR MESSAGES: MISSING FILENAME(S) You must enter two filenames after the KED command. BAD LOCATION FOR BEGIN You can only enter a BEGIN after THEN, ELSE, WHILE or ITERATE. BAD LOCATION FOR BEGINNING-OF-EXECUTION (BX) BEGINNING-OF-EXECUTION (BX) can only follow BEGINNING-OF-PROGRAM or a complete definition. STRUCTURE NOT A COMPOUND STATEMENT An END must match a BEGIN and if more than one instruction follows a THEN, ELSE, WHILE or ITERATE it must be part of a compound statement. BAD LOCATION FOR END PGM END-OF-EXECUTION (NDX) can only be typed after all constructs have been ended. ELSE NOT PAIRED WITH THEN Remember to do an NDC if THEN is not followed by a compound statement. COMMAND CAN'T BE INSERTED BEGINNING-OF-EXECUTION and END-OF-EXECUTION cannot be inserted. END REQUIRED It isn't necessary to type an NDC to end a construct that contains a compound statement. After END is typed an NDC is automatically performed by KED. ALREADY IN INSERT MODE Typing "i" while in insert mode will produce this message. INSERT ONLY AFTER END OF PROGRAM Insert mode can only be used after END-OF-EXECUTION (NDX) has been added. CAN'T INSERT INSIDE CONSTRUCT See insert restrictions. LAST POSSIBLE LEVEL NDC can't be performed beyond the last construct. PLEASE COMPLETE CONSTRUCT Exit from the insert mode is not allowed until all constructs are completed. BAD LOCATION FOR DEFINITION A definition can only follow BEGINNING-OF-PROGRAM or a complete definition. MAXIMUM NUMBER OF DEFINITIONS EXCEEDED A fixed number of definitions are allowed, even if some have been deleted so that fewer than the maximum actually remain in the program. Saving the program, quitting the editor and then invoking KED will allow additional definitions to replace those deleted in the earlier session, although you still may not have more than the allowable number definitions in a program. MAXIMUM NUMBER OF USES OF DEFINTION EXCEEDED Only a fixed number of uses of each definition is allowed in your program. INVALID TEST The menu lists valid KED commands for tests. No spaces should precede or follow tests; a backspace or a control character will produce an error. NEW NAME MUST BE UNIQUE Each user-defined name must be different from KAREL's instructions, tests and the edit commands. Although you may use any number of characters, only the first eight will be recognized. INVALID CHARACTERS IN NEW NAME Only letters, numbers and hyphens may be used in a new name and the first character must be a letter. INVALID COMMAND Be sure to type commands correctly. It doesn't matter whether you use capital or small letters but spaces before or after entries, the backspace or any control character will all produce an error. INSERT ONLY After END-OF-EXECUTUION (NDX) has been added, the only way to add instructions is to enter the insert mode. BAD LOCATION FOR COMMAND An improper location has been chosen for a command. CAN'T BE DELETED BEGINNING-OF-PROGRAM, BEGINNING-OF-EXECUTION, and END-OF-EXECUTION cannot be deleted. USER'S GUIDE FOR KAREL BATCH FILE A World-Builder and Simulator for KAREL the Robot After a program has been written using KED (a syntax-directed editor for KAREL the Robot), to create the world in which the program will be run and to execute the program, type: karel filename1 filename2 Filename1 should contain the file created in KED. Filename2 is used to store KAREL's world. If filename2 is a new file, an "empty world" will be printed. If filename2 is an old file, the previously created world it contains will be printed. Along with the new or old world, KAREL's street, avenue and direction and the number of beepers in his beeper bag will be shown. Then you will be asked if you want to change KAREL's location, beeper locations or wall location. If by mistake an old filename is given that does not contain an old world, you can exit gracefully by not saving the world. After a few system messages, you can start over and no damage will have been done to your old file. There are only ten streets (numbered 1 thru 10) and seventeen avenues (numbered 1 thru 17) in this representation of KAREL's world. Street 0, street 11, avenue 0 and avenue 18 entries will be accepted for wall building but are not legal locations for KAREL or beepers. Although any number of beepers can be carried in KAREL's beeper bag, only 9 may be put at any corner of his world. No error shutoff will occur if more than 9 are put at a given corner but only 9 will appear and a warning will be printed on the screen; these beepers are effectively lost to KAREL and cannot be recovered. The following prompts will be given for changes to KAREL's world; when entering a character (Y/N) only the character is required (no RETURN need be typed) but a number entry requires a RETURN. (1) CHANGE KAREL'S LOCATION? (Y/N) If "Y" is entered, you will be asked: KAREL'S STREET? KAREL'S AVENUE? DIRECTION? (N/S/E/W) At this point, KAREL will be shown on the screen. IS KAREL'S LOCATION CORRECT? (Y/N) If "N" is entered, the previous questions to change KAREL's location will be repeated. If "Y" is entered or if "N" is entered in response to (1) above, you will be asked: (2) CHANGE BEEPERS IN WORLD? (Y/N) If "Y" is entered, you will be asked: STREET? AVENUE? ENTER A TO ADD OR D TO DELETE BEEPER At this point the beeper will be added or deleted from the world. If a beeper has been added, you will be asked: IS BEEPER LOCATION CORRECT? (Y/N) If "N" is entered, the beeper questions will be repeated. If "Y" is entered or if a beeper has been deleted, you will be asked: OTHER BEEPER LOCATIONS? (Y/N) If "Y" is entered, the beeper questions will be repeated. If "N" is entered, you will be asked: (3) CHANGE BEEPERS IN BAG? (Y/N) If "Y" is entered, you will be asked: HOW MANY BEEPERS IN BEEPER BAG? 0 BEEPERS IN BAG, CORRECT? (Y/N) Here the number of beepers entered or 0 will be printed; any non-number will be interpreted as 0. Since typing errors cannot be corrected, simply enter "N". If "N" is entered, the beeper bag questions will be repeated. If "Y" is entered or if "N" is entered in response to (2), you will be asked: (4) CHANGE WALL LOCATIONS? (Y/N) IF "Y" is entered, you will be asked: BETWEEN WHAT STREETS? ? BETWEEN WHAT AVENUES? ? A number followed by a RETURN should follow each "?". If a number outside the accepted values for streets or avenues is entered, that question will be repeated. If the difference between the streets is one, the wall is assumed to be horizontal. ENTER A TO ADD OR D TO DELETE WALL At this point you can see the addition or deletion of the wall; a "+" will appear at corners. IS WALL LOCATION CORRECT? (Y/N) If "N" is entered, the wall will be erased and the wall questions will be repeated. If "Y" is entered, you will be asked: IS THIS THE LAST WALL? (Y/N) If "N" is entered, the wall questions will be repeated. If "Y" is entered or if "N" was entered in response to (3), you will be asked: (5) ANY FURTHER CHANGES TO THE WORLD? (Y/N) IF "Y" is entered, all the questions will be repeated starting with (1). If "N" is entered, you will be asked: (6) EXECUTE PROGRAM? (Y/N) If "Y" is entered, the world will be saved in filename2 and the tree in filename1 will be translated. After a few system messages are printed, the initial state of the world will be printed and KAREL's execution of the program will be shown on the screen. If there are problems (the wrong file was used for filename2, for instance) then you may enter "N". You will then be asked: EXIT KAREL? (Y/N) If "Y" is entered then after a few system messages the program will end. If "N" is entered, you will be asked again if you want to save the world (and start program execution). As KAREL executes your program, his direction is printed at the street and avenue of his current location, unless beepers are also located there. If both KAREL and any beepers are at the same corner, only @ (one beeper), 2 (2 beepers), etc. will be shown. When the execution has been completed successfully, "END OF EXECUTION" will be printed and the final state of the world will remain on the screen, along with KAREL's street, avenue, direction and the number of beepers in his beeper bag at the end of execution. At this point, you may invoke KED to make any changes in your program then run the new syntax tree and the old world and try again. If an error shutoff occurs, the program will be terminated and one of the following messages will be printed: 1. FRONT IS BLOCKED A move was attempted while KAREL was facing a wall. 2. NO BEEPERS IN BAG A putbeeper was attempted while there were no beepers in KAREL's beeper bag. 3. NO BEEPERS ON CORNER A pickbeeper was attempted at a location where there were no beepers. 4. NO TURNOFF EXECUTED The final turnoff instruction was omitted from the program. You may study the state of the world which produced the error and then invoke KED to make appropriate changes to your program and try another run.