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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))))))
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