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+;;; "comparse.scm" Break command line into arguments.
+;Copyright (C) 1995 Aubrey Jaffer
+;
+;Permission to copy this software, to redistribute it, and to use it
+;for any purpose is granted, subject to the following restrictions and
+;understandings.
+;
+;1.  Any copy made of this software must include this copyright notice
+;in full.
+;
+;2.  I have made no warrantee or representation that the operation of
+;this software will be error-free, and I am under no obligation to
+;provide any services, by way of maintenance, update, or otherwise.
+;
+;3.  In conjunction with products arising from the use of this
+;material, there shall be no use of my name in any advertising,
+;promotional, or sales literature without prior written consent in
+;each case.
+
+;;;; This is a simple command-line reader.  It could be made fancier
+;;; to handle lots of `shell' syntaxes.
+
+(require 'string-port)
+(define (read-command . port)
+  (define argv '())
+  (define obj "")
+  (define chars '())
+  (define eof #f)
+  (define readc (lambda () (read-char port)))
+  (define peekc (lambda () (peek-char port)))
+  (define s-expression
+    (lambda ()
+      (splice-arg (call-with-output-string
+		   (lambda (p) (display (slib:eval (read port)) p))))))
+  (define (backslash goto)
+    (readc)
+    (cond ((char=? #\newline (peekc)) (readc) (goto (peekc)))
+	  (else (set! chars (cons (readc) chars))
+		(build-token (peekc)))))
+  (define loop
+    (lambda (c)
+      (case c
+	((#\\) (backslash loop))
+	((#\") (splice-arg (read port)))
+	((#\( #\') (s-expression))
+	((#\#)
+	 (do ((c (readc) (readc)))
+	     ((or (eof-object? c) (char=? #\newline c) c))))
+	((#\; #\newline) (readc))
+	(else
+	 (cond ((eof-object? c) c)
+	       ((char-whitespace? c) (readc) (loop (peekc)))
+	       (else (build-token c)))))))
+  (define splice-arg
+    (lambda (arg)
+      (set! obj (string-append obj (list->string (reverse chars)) arg))
+      (set! chars '())
+      (build-token (peekc))))
+  (define build-token
+    (lambda (c)
+      (case c
+	((#\") (splice-arg (read port)))
+	((#\() (s-expression))
+	((#\\) (backslash build-token))
+	((#\newline #\;)
+	 (readc)
+	 (set! argv (cons (string-append
+			   obj (list->string (reverse chars)))
+			  argv)))
+	(else
+	 (cond ((or (eof-object? c)
+		    (char-whitespace? c))
+		(readc)
+		(set! argv (cons (string-append
+				  obj (list->string (reverse chars)))
+				 argv))
+		(set! obj "")
+		(set! chars '())
+		(loop (peekc)))
+	       (else (set! chars (cons (readc) chars))
+		     (build-token (peekc))))))))
+  (set! port
+	(cond ((null? port) (current-input-port))
+	      ((= 1 (length port)) (car port))
+	      (else
+	       (slib:error
+		'read-command-line
+		"Wrong Number of ARGs:"
+		port))))
+  (let ((c (loop (peekc))))
+    (cond ((and (null? argv) (eof-object? c)) c)
+	  (else (reverse argv)))))