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+;; introspection.scm -- name says it all
+
+;; Copyright (C) 2009 Jose Antonio Ortega Ruiz
+
+;; Author: Jose Antonio Ortega Ruiz <jao@gnu.org>
+;; Start date: Sun Feb 08, 2009 18:44
+
+;; This file is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This file is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Comentary:
+
+;; Procedures introspecting on scheme objects and their properties.
+
+;;; Code:
+
+(define-module (geiser introspection)
+  #:export (proc-args completions)
+  #:use-module (system vm program)
+  #:use-module (ice-9 session)
+  #:use-module (srfi srfi-1))
+
+(define (proc-args proc)
+  (let ((proc (and (symbol? proc)
+                   (module-bound? (current-module) proc)
+                   (eval proc (current-module)))))
+    (cond ((not proc) #f)
+          ((program? proc) (program-args proc))
+          ((procedure? proc) (procedure-args proc))
+          ((macro? proc) (macro-args proc))
+          (else #f))))
+
+(define (program-args program)
+  (let* ((arity (program-arity program))
+         (arg-no (first arity))
+         (opt (> (second arity) 0))
+         (args (map first (take (program-bindings program) arg-no))))
+    (format-args (if opt (drop-right args 1) args)
+                 (and opt (last args))
+                 (program-module program))))
+
+(define (procedure-args proc)
+  (let* ((arity (procedure-property proc 'arity))
+         (req (first arity))
+         (opt (third arity))
+         (env (procedure-environment proc)))
+    (format-args (map (lambda (n)
+                        (string->symbol (format "arg~A" (+ 1 n))))
+                      (iota req))
+                 (and opt 'rest)
+                 (and (not (null? env)) env))))
+
+(define (macro-args macro)
+  (let ((prog (macro-transformer macro)))
+    (if prog
+        (program-args prog)
+        (format-args '(...) #f #f))))
+
+(define (format-args args opt module)
+  (list (cons 'required args)
+        (cons 'optional (or opt '()))
+        (cons 'module (if module (module-name module) '()))))
+
+(define (completions prefix)
+  (sort! (map symbol->string
+              (apropos-internal (string-append "^" prefix)))
+         string<?))
+
+;;; introspection.scm ends here