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+;;"coerce.scm" Scheme Implementation of COMMON-LISP COERCE and TYPE-OF.
+; Copyright (C) 1995, 2001 Aubrey Jaffer
+;
+;Permission to copy this software, to modify it, to redistribute it,
+;to distribute modified versions, 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.
+
+;;@body
+;;Returns a symbol name for the type of @1.
+(define (type-of obj)
+  (cond
+   ;;((null? obj)		'null)
+   ((boolean? obj)	'boolean)
+   ((char? obj)		'char)
+   ((number? obj)	'number)
+   ((string? obj)	'string)
+   ((symbol? obj)	'symbol)
+   ((input-port? obj)	'port)
+   ((output-port? obj)	'port)
+   ((procedure? obj)	'procedure)
+   ((eof-object? obj)	'eof-object)
+   ((list? obj)		'list)
+   ((pair? obj)		'pair)
+   ((and (provided? 'array) (array? obj))	'array)
+   ((and (provided? 'record) (record? obj))	'record)
+   ((vector? obj)	'vector)
+   (else		'?)))
+
+;;@body
+;;Converts and returns @1 of type @code{char}, @code{number},
+;;@code{string}, @code{symbol}, @code{list}, or @code{vector} to
+;;@2 (which must be one of these symbols).
+(define (coerce obj result-type)
+  (define (err) (slib:error 'coerce 'not obj '-> result-type))
+  (define obj-type (type-of obj))
+  (cond
+   ((eq? obj-type result-type) obj)
+   (else
+    (case obj-type
+      ((char)   (case result-type
+		  ((number integer) (char->integer obj))
+		  ((string) (string obj))
+		  ((symbol) (string->symbol (string obj)))
+		  ((list)   (list obj))
+		  ((vector) (vector obj))
+		  (else     (err))))
+      ((number) (case result-type
+		  ((char)   (integer->char obj))
+		  ((atom)   obj)
+		  ((integer) obj)
+		  ((string) (number->string obj))
+		  ((symbol) (string->symbol (number->string obj)))
+		  ((list)   (string->list (number->string obj)))
+		  ((vector) (list->vector (string->list (number->string obj))))
+		  (else     (err))))
+      ((string) (case result-type
+		  ((char)   (if (= 1 (string-length obj)) (string-ref obj 0)
+				(err)))
+		  ((atom)   (or (string->number obj) (string->symbol obj)))
+		  ((number integer) (or (string->number obj) (err)))
+		  ((symbol) (string->symbol obj))
+		  ((list)   (string->list obj))
+		  ((vector) (list->vector (string->list obj)))
+		  (else     (err))))
+      ((symbol) (case result-type
+		  ((char)   (coerce (symbol->string obj) 'char))
+		  ((number integer) (coerce (symbol->string obj) 'number))
+		  ((string) (symbol->string obj))
+		  ((atom)   obj)
+		  ((list)   (string->list (symbol->string obj)))
+		  ((vector) (list->vector (string->list (symbol->string obj))))
+		  (else     (err))))
+      ((list)   (case result-type
+		  ((char)   (if (and (= 1 (length obj))
+				     (char? (car obj)))
+				(car obj)
+				(err)))
+		  ((number integer)
+		   (or (string->number (list->string obj)) (err)))
+		  ((string) (list->string obj))
+		  ((symbol) (string->symbol (list->string obj)))
+		  ((vector) (list->vector obj))
+		  (else     (err))))
+      ((vector) (case result-type
+		  ((char)   (if (and (= 1 (vector-length obj))
+				     (char? (vector-ref obj 0)))
+				(vector-ref obj 0)
+				(err)))
+		  ((number integer)
+		   (or (string->number (coerce obj string)) (err)))
+		  ((string) (list->string (vector->list obj)))
+		  ((symbol) (string->symbol (coerce obj string)))
+		  ((list)   (list->vector obj))
+		  (else     (err))))
+      (else (err))))))