recognizers
A collection of recognizers
- raw README.md
- raw Recognizer.4th
- raw Stack.4th
- raw literacy.4th
- raw package.4th
- raw rec-double-paren.4th
- raw rec-find.4th
- raw rec-name.4th
- raw rec-notfound.4th
- raw rec-num.4th
- raw rec-string.4th
- raw rec-time.4th
- raw tester.fs
Recognizers
Matthias Trute mtrute@web.de Version 2.0.0 - 2017-01-28
This package is a collection of recognizer examples. To play with them a simple implementation is provided. It works unchanged on (old) gforth's, swiftforth and VFX. They are not (yet) able to compile code or are otherwise integrated into the underlying system.
Many examples contain test units that illustrate what the recognizer does.
More information about recognizers can be found at http://amforth.sourceforge.net/Recognizers.html and http://forth200x.org
Running the examples with e.g. gforth should not
give any errors beside a possible redefinition of {
$ gforth rec-double-paren.4th
redefined { Gforth 0.7.2, Copyright (C) 1995-2008 Free Software Foundation, Inc.
Gforth comes with ABSOLUTELY NO WARRANTY; for details type `license'
Type `bye' to exit
bye
$
The code examples use rev 4 of the recognizer RFD. Package version 1.x use the rev 3 of it.
Recognizer.4th
This file in combination with Stack.4th
gives a
playground for making experiments with recognizers. It
has been tested with gforth versions that currently
come with the linux distributions, MPE's vfxlin
and Forth Inc's Swiftforth for linux.
rec-num.4th
This file contains four recognizers. They deal with
numbers in various formats and use >NUMBER
for the
actual number conversion.
rec:char ( addr len -- n dt:num | dt:null )
Forth 2012 defined the 'c' syntax for single characters.
That means that char c
or [char] c
can be replaced
with 'c'
.
rec:snum ( addr len -- n dt:num | dt:null )
This recognizer handles single cell numbers. It checks whether a strings consists of digits only and that the value range of the number fits into a single cell. The sign and base prefix characters work as expected.
rec:dnum ( addr len -- d dt:dnum | dt:null )
This recognizer handles double cell numbers. It accepts the standard double number format: digits with a trailing dot in addition to the base prefix and sign character.
These three recognizers are combined into the rec:num
recognizer that may be used to handle all number formats
in one call.
rec-find.4th
This file contains a dictionary lookup recognizer. It uses
FIND
for the actual work thus uses the search order if
present.
rec-name.4th
Another dictionary lookup recognizer. This one does not
depend on FIND
and searches the standard forth wordlist
only. It returns name tokens instead of execution tokens.
It requires TRAVERSE-WORDLIST
and the NAME>x
words
from Forth 2012 to work. From the future, quotations are
used too.
rec-string.4th
Uses "
as the string delimiter. Everything
between two "
within SOURCE
is a string.
It can replace the forth command S"
completly.
Instead of S" foo"
use "foo"
. The space
after S"
is no longer needed, it is now part
of the string. S" foo"
and " foo"
differ with the leading space in the latter.
The string lives as long as SOURCE
is
unchanged! More sophisticated implementations
may use a string stack. Compilation to the
dictionary is done by SLITERAL
. Postponing
throws an exception simply because that
is not specified in the standard.
A typical use is
"hello world" type
hello world
: test "hello world" type ; test
hello world
that prints the string resp. compiles it and prints it at runtime.
rec-notfound.4th
This is not really a recognizer but an API wrapper for
the often found not-found
hook. It discards any input
and calls a deferred word not-found
. This word is
expected to never return properly by e.g. printing an
error message and throwing an exception.
With this recognizer as the last one in the stack, programs that use the not-found hook can easily adapted.
rec-double-paren.4th
Implements the multiline ((
))
comment block.
The ((
switches the system recognizer stack to
one that searches only one otherwise hidden wordlist.
This wordlist contains only words that are allowed
to be executed in comments. For now only ))
that
switches back to normal operation.
Since the recognizer stack switch is unaffected from
REFILL
operations, multiline comments work too.
This recognizer needs a system that has recognizers
native support. It does not depend on SOURCE
however.
It re-uses the REFILL-PARSE-EVALUATE loop found in
the text interpreter. Some tests are provided.
literacy.4th
Simple formatting of source code in the spirit von Don Knuth' literate programming. You can combine the real source code and its documentation in one file that the standard forth interpreter can handle directly.
Actually testing this recognizer requires a Forth that supports recognizers already.
Author: Julian Fondren, 2014 License: probably public domain.
rec-time.4th
check and convert for the hh:mm:ss notation returning a double cell number for the number of seconds it represents.