Power-Programmierung/CD1.mdf/forth/compiler/love/chap02.doc

Text File | 1993-04-11 | 12KB | 247 lines

Chapter2                L_O_V_E FORTH



2.0  Compiling source code
     ---------------------


    L.O.V.E Forth allows considerable flexibility in the forms of
source code that it accepts. Programs can be loaded from screen format
floppy disks, or screen files and text files under MS-DOS.  These may be
intermixed as desired and nested within each other, up to ten levels deep.

         Many file words are named with a quote following (eg.
INCLUDE", OPEN" ).  These words are followed by a file name, or a path
and file name (eg.  INCLUDE"    MYFILE.TXT   or   OPEN"
\WORK\SCREENS\PROG.SCR).  There should always be a closing quote (it
may be omitted when it is the last item on a line that has been keyed
in).  The word   "CLOSE, however, does not use a name. In this article,
the words   BLOCK   and SCREEN are used interchangeably, both meaning a
1024 character fixed unit of disk storage.

         In order to load source code from screen format files or floppy
disks, the block handling words must be loaded.  To load them, type:
INCLUDE"     LOADBLK.TXT .    Once loaded, they may NOT be removed, as
some kernel words are REDEFINED.


2.1  Loading MS-DOS text files
     -------------------------

     Text files are convenient and efficient in use of disk space.
Therefore L.O.V.E. Forth accepts source code from text files.  The word
INCLUDE"     followed by MS-DOS path and file name, loads the specified
file. There is a file size limit of 65535 bytes.

    Stand-alone editors are accommodated by the L.O.V.E. Forth DOS
command.  Typing DOS, followed by the path and name of the desired text
editor, begins an editing session.  To return to Forth, simply save the
work, exit the editor, and load the desired file.

         There are several methods of commenting available in text
files.  The usual Forth comment   ( )     works to a length of 256
characters.  The line comment function     \     works for one line
(until carriage return is encountered).  To comment out large portions
of the text, the words   (( and ))     are available.  They may
enclose any amount of space, and may be used around ( ) and \ .   They
may not be nested within themselves.  To comment from one point to the
end of the file, simply use (( without providing a closing )).   Note
that )) is a Forth word and must be surrounded by spaces or
end-of-line, return or enter.

         The word   EXIT   is often used to exit from the compilation of
a Forth screen.  Because of this, it may not be used for this function
in text files.   Simply use (( as is described above.   In addition,
the words --> ,  LOAD"    and    THRU"    may not appear in text files
as well.  LOAD"   and   THRU"   may be used instead to load screens
from another file.


Example:
     LOAD" example.scr"   or   THRU" example.txt"


     It is possible to load a screen file with   INCLUDE" .    In this
case, however, it must not include any of the words described above or
the Forth line comment     \     .

     If an error occurs while loading a text file, the previous
twenty-four successfully loaded lines are displayed, and the erroneous
word is highlighted.


2.2  Using screen files
     ------------------

     L.O.V.E. Forth supports editing and loading of screen files.  A
comprehensive screen editor and numerous utilities for screen handling
are supplied.  The maximum file size accomodated is 32767 screens.

     The word   OPEN"   followed by a filename, opens an existing screens
file for editing.  It becomes the 'current' file, which is accessed by
block disk words such as   BLOCK    UPDATE   and   LINE

     To show contents of a screen on the display, there is a
fast LISTing utility.  Type:   (screen-no) L   to list a screen.  The
words LN, LB list one screen forward and backward respectively,   LL
relists the current screen.   The word   EL   enters the full-screen screen
editor at the current screen.

     The screen editor is a virtual vocabulary.  It may be entered at
the current screen with   EL   or by:  (screen-no) EDIT   .
Typing control-X   displays the help information.
This editor provides facilities for general editing, 'gobbling' lines
or words to a buffer, and moving from  screen to screen.
To save the screen and exit from the editor, type:  ESCAPE and  F keys.
Note that the 'gobble' buffers are lost if any compiling is performed,
or if another virtual vocabulary is called in.  Do not use the editor
on a write-protected disk, as it always writes the current screen, when
moving between screens.

     To load from the current file, the words   LOAD"   and   THRU"   may
be used. It is possible to load right from the editor by typing escape   L .
Arrow  -->  may be included to proceed to the next screen and   EXIT   may
be used to terminate loading at a point on a screen.  If any error
occurs during loading, the erroneous screen becomes the current screen
for listing and editing.  The word   WHERE   will display the screen with
the erroneous word highlighted.

     The word   SHOW  performs the rapid listing of a range of screens.
To slow it down, store a value into the variable   SHOWDELAY.   INDEX
prints the first line only, from a range of screens.

     To create a new screens file, the word   OPEN-NEW"   followed by a
path and file name is used.  It gives the file a starting size of two
screens.  To obtain a larger file size, type:  (total screens) SCREENS .
When in the editor, the file can also be extended, simply by advancing
past the last screen in the file.  To open a different file, simply use
OPEN"   or   OPEN-NEW".   The previous file is automatically closed.  To
close the file explicitly, the word   "CLOSE   may be used (no word
preceeds it).

     To copy a range of screens from one place on disk to another, the
word   COPYSCRNS   may be used.  Pass in the starting screen, ending screen
and destination screen.  Screens may be 'slid up' or down in the current
file.  To erase a range of screens, the word   ERASESCRNS   is used (pass in
start and end screens).  To put a header, with date time and screen
number on a range of screens, use the word   SCRNHDS.

     To copy screens from file to file, the word   COPYF->F"   is used.
Pass in the starting screen and ending screen in the source file, and
the first destination screen in the destination file.  Follow this word
with the source path\file and the destination path\file. For example:

        0 10 5  COPYF->F"\my-dir\file1.scr"myfile.scr"
        There should be no space following the second " mark.

     To load a screen or range of screens from any screen file, the
words   LOAD"   and   THRU"   may be used.   The values passed in are
the same as  for LOAD and THRU, but the screens are loaded from the
specified file.  The words -->   LOAD   THRU   may be used in the
loaded file and operate within that file.  Additional files may be
loaded from within those files with additional   INCLUDE"   LOAD"   or
THRU"   commands.

     If an error occurs while loading a screens file, that file is
left open for editing at the erroneous screen.  If an error occurs
while loading a text file, no file is left open for editing.  If there
are no errors, the file currently open before the loading remains so.

     Screen files may be converted to text files for more convenient
programming.  The free-ware program    BUNBLOCK.EXE   is provided for
this purpose.  Type   BUNBLOCK   with no arguments for help.


2.3  Using screens format diskettes
     ------------------------------

     The traditional Forth source code storage is on floppy disks
dedicated entirely to sequential screens. L.O.V.E. Forth supports both
editing and loading of eight and ten sector formats.  Disks are accessed
by bypassing MS-DOS.  Hard disks are not accessed.  There are also
several utilities for conversion of screen floppies to screen files.
The screen format facility must be explicitly enabled before use, as
follows.

     When no screen file is open, Forth accesses the floppy disks in
screen format.  All the block disk words and utilities described
above may be used   LOAD   THRU  -->  SHOW   INDEX   WHERE   COPYSCRNS
and  ERASESCRNS  .   In addition the words   LOAD"   THRU"   and
INCLUDE" may appear on screens format diskette screens.

     There are two formats floppy screens available:  8 sectors
per track and 10 sectors per track (320 or 400k per disk).  The former
is the default setting.  To switch to and from 10 sectors, format the
commands   10-SECTS-ON   and   10-SECTS-OFF   These are used
(in   SCREEN-UTILS  vocabulary).  Floppy drives are treated as having
contiguous screens.  Screen 319 (399) is the last screen on drive A:,
and screen 320 (400) is the first on drive B:.   Note that accesses to
floppies through MS-DOS functions confuse the screens format utilities
(sets them to 9 sectors/track).  Two solutions to this: Refrain from
using floppies for MS-DOS functions or switch to screen files.  Using
virtual vocabularies from MS-DOS floppies will not cause problems.

     While a screens file is in use, and it is desired to list a
single screen on a screens format floppy, use the command:
    (scrn_no) LSCRN
To copy from a screens format floppy to a screens file, the command
COPYSCRNS->F"   followed by the path\file of an existing file is used.
The starting screen, ending screen, and destination screen are passed
in.   It is also possible to copy from a screens file to floppy screens
with the command:   COPYF->SCRNS" followed by the source file, and with
similar arguments passed in.

     INITDISK   will initialize a screens format floppy disk to the
current sectors/track setting.  This word normally initializes drive B:.
To initialize drive A:, execute the word   SETDRIVES,  which prompts the
drive to use the word,   COPYDISK,   copies the entire disk from drive A:
to B:, and the word   COMPDISK   compares the two (two drives are required
for both words).  The word   COPYNEW   initializes drive B:, copies drive
A: to B: and compares the two.

     The variable   BLKMAX   is used with screens format diskettes to set
the maximum available screen.  If it is desirable to limit the action of
editing, listing etc,  set this variable to the last usable block#.  The
variable   OFFSET   is also used primarily with screens format diskettes.
Its contents are simply added to the block number on block operations.
For example, to make screen 0 refer to the first block on drive B,
type:  0 ONB   OFFSET !

     Normally usage of screens floppy diskettes is disabled.  To
enable the usage of these obsolete media, type:
        SCREEN-UTILS ENABLE-SCRNS .
To disable use:
        SCREEN-UTILS DISABLE-SCRNS .
These changes may be made permanent by doing a SAVE" of the Forth
system.


2.4  Nested loading capability
     -------------------------

     L.O.V.E. Forth allows files to be loaded from within other files.
This permits screen files and text files to be intermixed and
nested ten levels deep.  Simply include the appropriate loading
word (eg.    LOAD"    or    INCLUDE"   )   in a screen or file.

                              Load the following:
                         Screen disk:   Screen file   Text file:
From:   Screen disk          *              *             *
        Screen file                         *             *
        Text file                           *             *