13.22 guile-tools lexer-repl

Usage: lexer-repl [--emacs] [--offset N] input spec

lexer-repl provides a read-eval-print loop specialized for lexical
analysis of the INPUT file using a grammar specified in the SPEC
file.  The SPEC file is regular Guile scheme code that also defines a
grammar, and calls `set-LEXER-SPEC!' with it.

The INPUT file should be in a format that can be analyzed using the
spec (otherwise you may see many errors!).  Option "--emacs" means
don't show a prompt but instead echo the input in a way suitable for
feeding to Emacs' `read' function.  Option "--offset N" means to
ignore the first N characters.

Usage from a Scheme program:
 (lexer-repl under-emacs? lexer inp)

If UNDER-EMACS? is non-#f, lexer-repl does not display a prompt,
but instead displays, after input, a "pseudo-prompt" followed by
the input, designed to be comment-like (transparent) to the `read'
function in emacs.  LEXER is a lexical analyzer conforming to that
returned by `make-lexer' in module (lang lex).  INP is an input
port conforming to that returned by `make-line-buffering-input-port'
in module (ice-9 lineio).  This port is used to read the INPUT file,
and should not be confused w/ current-input-port, from which commands
are read.

Commands:

(next) --- Display the next lexeme to stdout followed by newline.
           Lexemes have the form: (LENGTH NAME MATCHED-INPUT)
           where NAME is a symbol, MATCHED-INPUT is a string and
           LENGTH is the count of characters in the string.  The
           spec file may arrange to omit MATCHED-INPUT by using
           a "procedure action".  For example, given the rules:

             ("<<"  double-less-than)
             ("--"  ,(lambda ignored 'double-dash))
             (">>"  ,(lambda ignored '(double-greater)))

           and given input ">>--<<", lexer-repl displays:

             (2 double-greater)
             (2 . double-dash)
             (2 double-less-than "<<")

           on three subsequent invocations of the `(next)' command.

(quit) --- Quit the repl.

TODO:
 - Add "--stop N" option.
 - Add commands to examine/reset stats.