marcomaggi wrote:
FWIW I started repackaging SILex[1] by Danny Dube' into Nausicaa.
To make it work with R6RS I had to change almost nothing, I only
wrapped the file "silex.scm" into a LIBRARY form with the following
incipit:
(library (silex)
(export lex lex-tables)
(import (rnrs)
(rnrs mutable-pairs)
(rnrs mutable-strings)
(rnrs r5rs))
and commented out the internal implementation of
STRING-DOWNCASE.
I just got around to trying this out and wanted to confirm, it works
like a charm. I.e. also the calculator demo you posted below (Tested in
Ikarus) Thanks for investigating this Marco.
Ed
[1] <http://www.iro.umontreal.ca/~dube/>
As a usage example, put the following in a file called
"calculator.l":
blanks [ \n\t]+
decint [0-9]+
binint #[bB][01]+
octint #[oO][0-7]+
hexint #[xX][0-9A-Fa-f]+
integer {decint}|{binint}|{octint}|{hexint}
exponent ([eE][+\-]?[0-9]+)
truereal [0-9]+\.|[0-9]*\.[0-9]+{exponent}?|[0-9]+{exponent}
real {truereal}|{integer}
imag ({decint}|{real})i
nan \-nan\.0|\+nan\.0
inf \-inf\.0|\+int\.0
initial [a-zA-Z!$&:<=>?_~]
subsequent {initial}|[0...@]
symbol {initial}{subsequent}*
operator [\+\-*/%\^\\]
comma ,
oparen \(
cparen \)
paren {oparen}|{cparen}
%%
{blanks} ;; skip blanks, tabs and newlines
{imag} (string->number (string-append "+" yytext))
{real} (string->number yytext)
{nan} (string->number yytext)
{inf} (string->number yytext)
{operator} (case (string-ref yytext 0)
((#\+) +)
((#\-) -)
((#\*) *)
((#\/) /)
((#\%) mod)
((#\^) expt))
{symbol} (string->symbol yytext)
{comma} (parse-comma)
{paren} (string-ref yytext 0)
<<EOF>> (parse-eof)
process it with the following program:
(import (rnrs)
(silex))
(lex "calculator.l" "calculator.l.sls")
put the file "calculator.l.sls" into a Scheme program, with the
following tail:
(lexer-init 'string "1+23e-45+678.9e12*(4113+23i) / sin 545 + tan(1,
2)")
(define (parse-eof)
#f)
(define (parse-comma)
cons)
(do ((token (lexer) (lexer)))
((not token))
(display token)
(newline))
enjoy the output.
--
Marco Maggi
