234 lines
8.4 KiB
Scheme
234 lines
8.4 KiB
Scheme
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;;; srfi-37.scm --- args-fold
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;; Copyright (C) 2007, 2008, 2013 Free Software Foundation, Inc.
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;;
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;; This library is free software; you can redistribute it and/or
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;; modify it under the terms of the GNU Lesser General Public
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;; License as published by the Free Software Foundation; either
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;; version 3 of the License, or (at your option) any later version.
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;;
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;; This library is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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;; Lesser General Public License for more details.
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;;
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;; You should have received a copy of the GNU Lesser General Public
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;; License along with this library; if not, write to the Free Software
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;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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;;; Commentary:
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;;
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;; To use this module with Guile, use (cdr (program-arguments)) as
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;; the ARGS argument to `args-fold'. Here is a short example:
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;;
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;; (args-fold (cdr (program-arguments))
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;; (let ((display-and-exit-proc
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;; (lambda (msg)
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;; (lambda (opt name arg)
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;; (display msg) (quit) (values)))))
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;; (list (option '(#\v "version") #f #f
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;; (display-and-exit-proc "Foo version 42.0\n"))
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;; (option '(#\h "help") #f #f
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;; (display-and-exit-proc
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;; "Usage: foo scheme-file ..."))))
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;; (lambda (opt name arg)
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;; (error "Unrecognized option `~A'" name))
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;; (lambda (op) (load op) (values)))
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;;
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;;; Code:
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;;;; Module definition & exports
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(define-module (srfi srfi-37)
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#:use-module (srfi srfi-9)
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#:export (option option-names option-required-arg?
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option-optional-arg? option-processor
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args-fold))
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(cond-expand-provide (current-module) '(srfi-37))
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;;;; args-fold and periphery procedures
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;;; An option as answered by `option'. `names' is a list of
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;;; characters and strings, representing associated short-options and
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;;; long-options respectively that should use this option's
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;;; `processor' in an `args-fold' call.
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;;;
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;;; `required-arg?' and `optional-arg?' are mutually exclusive
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;;; booleans and indicate whether an argument must be or may be
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;;; provided. Besides the obvious, this affects semantics of
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;;; short-options, as short-options with a required or optional
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;;; argument cannot be followed by other short options in the same
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;;; program-arguments string, as they will be interpreted collectively
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;;; as the option's argument.
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;;;
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;;; `processor' is called when this option is encountered. It should
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;;; accept the containing option, the element of `names' (by `equal?')
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;;; encountered, the option's argument (or #f if none), and the seeds
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;;; as variadic arguments, answering the new seeds as values.
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(define-record-type srfi-37:option
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(option names required-arg? optional-arg? processor)
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option?
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(names option-names)
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(required-arg? option-required-arg?)
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(optional-arg? option-optional-arg?)
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(processor option-processor))
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(define (error-duplicate-option option-name)
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(scm-error 'program-error "args-fold"
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"Duplicate option name `~A~A'"
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(list (if (char? option-name) #\- "--")
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option-name)
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#f))
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(define (build-options-lookup options)
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"Answer an `equal?' Guile hash-table that maps OPTIONS' names back
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to the containing options, signalling an error if a name is
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encountered more than once."
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(let ((lookup (make-hash-table (* 2 (length options)))))
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(for-each
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(lambda (opt)
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(for-each (lambda (name)
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(let ((assoc (hash-create-handle!
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lookup name #f)))
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(if (cdr assoc)
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(error-duplicate-option (car assoc))
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(set-cdr! assoc opt))))
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(option-names opt)))
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options)
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lookup))
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(define (args-fold args options unrecognized-option-proc
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operand-proc . seeds)
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"Answer the results of folding SEEDS as multiple values against the
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program-arguments in ARGS, as decided by the OPTIONS'
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`option-processor's, UNRECOGNIZED-OPTION-PROC, and OPERAND-PROC."
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(let ((lookup (build-options-lookup options)))
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;; I don't like Guile's `error' here
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(define (error msg . args)
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(scm-error 'misc-error "args-fold" msg args #f))
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(define (mutate-seeds! procedure . params)
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(set! seeds (call-with-values
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(lambda ()
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(apply procedure (append params seeds)))
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list)))
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;; Clean up the rest of ARGS, assuming they're all operands.
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(define (rest-operands)
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(for-each (lambda (arg) (mutate-seeds! operand-proc arg))
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args)
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(set! args '()))
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;; Call OPT's processor with OPT, NAME, an argument to be decided,
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;; and the seeds. Depending on OPT's *-arg? specification, get
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;; the parameter by calling REQ-ARG-PROC or OPT-ARG-PROC thunks;
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;; if no argument is allowed, call NO-ARG-PROC thunk.
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(define (invoke-option-processor
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opt name req-arg-proc opt-arg-proc no-arg-proc)
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(mutate-seeds!
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(option-processor opt) opt name
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(cond ((option-required-arg? opt) (req-arg-proc))
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((option-optional-arg? opt) (opt-arg-proc))
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(else (no-arg-proc) #f))))
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;; Compute and answer a short option argument, advancing ARGS as
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;; necessary, for the short option whose character is at POSITION
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;; in the current ARG.
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(define (short-option-argument position)
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(cond ((< (1+ position) (string-length (car args)))
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(let ((result (substring (car args) (1+ position))))
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(set! args (cdr args))
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result))
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((pair? (cdr args))
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(let ((result (cadr args)))
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(set! args (cddr args))
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result))
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((pair? args)
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(set! args (cdr args))
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#f)
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(else #f)))
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;; Interpret the short-option at index POSITION in (car ARGS),
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;; followed by the remaining short options in (car ARGS).
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(define (short-option position)
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(if (>= position (string-length (car args)))
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(begin
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(set! args (cdr args))
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(next-arg))
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(let* ((opt-name (string-ref (car args) position))
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(option-here (hash-ref lookup opt-name)))
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(cond ((not option-here)
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(mutate-seeds! unrecognized-option-proc
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(option (list opt-name) #f #f
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unrecognized-option-proc)
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opt-name #f)
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(short-option (1+ position)))
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(else
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(invoke-option-processor
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option-here opt-name
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(lambda ()
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(or (short-option-argument position)
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(error "Missing required argument after `-~A'" opt-name)))
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(lambda ()
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;; edge case: -xo -zf or -xo -- where opt-name=#\o
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;; GNU getopt_long resolves these like I do
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(short-option-argument position))
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(lambda () #f))
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(if (not (or (option-required-arg? option-here)
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(option-optional-arg? option-here)))
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(short-option (1+ position))))))))
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;; Process the long option in (car ARGS). We make the
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;; interesting, possibly non-standard assumption that long option
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;; names might contain #\=, so keep looking for more #\= in (car
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;; ARGS) until we find a named option in lookup.
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(define (long-option)
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(let ((arg (car args)))
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(let place-=-after ((start-pos 2))
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(let* ((index (string-index arg #\= start-pos))
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(opt-name (substring arg 2 (or index (string-length arg))))
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(option-here (hash-ref lookup opt-name)))
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(if (not option-here)
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;; look for a later #\=, unless there can't be one
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(if index
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(place-=-after (1+ index))
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(mutate-seeds!
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unrecognized-option-proc
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(option (list opt-name) #f #f unrecognized-option-proc)
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opt-name #f))
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(invoke-option-processor
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option-here opt-name
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(lambda ()
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(if index
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(substring arg (1+ index))
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(error "Missing required argument after `--~A'" opt-name)))
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(lambda () (and index (substring arg (1+ index))))
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(lambda ()
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(if index
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(error "Extraneous argument after `--~A'" opt-name))))))))
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(set! args (cdr args)))
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;; Process the remaining in ARGS. Basically like calling
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;; `args-fold', but without having to regenerate `lookup' and the
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;; funcs above.
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(define (next-arg)
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(if (null? args)
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(apply values seeds)
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(let ((arg (car args)))
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(cond ((or (not (char=? #\- (string-ref arg 0)))
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(= 1 (string-length arg))) ;"-"
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(mutate-seeds! operand-proc arg)
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(set! args (cdr args)))
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((char=? #\- (string-ref arg 1))
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(if (= 2 (string-length arg)) ;"--"
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(begin (set! args (cdr args)) (rest-operands))
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(long-option)))
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(else (short-option 1)))
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(next-arg))))
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(next-arg)))
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;;; srfi-37.scm ends here
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