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|
#!r6rs
;;; FILE "tiny-talk-plus.sls"
;;; IMPLEMENTS Adds object support for Scheme values to tiny-talk.
;;; AUTHOR Ken [dot] Dickey [at] Whidbey [dot] Com
;;;COPYRIGHT (c) 2008 by Kenneth A Dickey. All rights reserved.
;;;
;;;Permission is hereby granted, free of charge, to any person
;;;obtaining a copy of this software and associated documentation
;;;files (the "Software"), to deal in the Software without
;;;restriction, including without limitation the rights to use,
;;;copy, modify, merge, publish, distribute, sublicense, and/or
;;;sell copies of the Software, and to permit persons to whom
;;;the Software is furnished to do so, subject to the following
;;;conditions:
;;;
;;;The above copyright notice and this permission notice shall
;;;be included in all copies or substantial portions of the Software.
;;;
;;;THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
;;;EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
;;;OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
;;;NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
;;;HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
;;;WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
;;;FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
;;;OTHER DEALINGS IN THE SOFTWARE.
;;;tiny-talk=plus
(library (tiny-talk-plus)
(export $ object define-predicate ->string object? field-spec ;; from tiny-talk
start-tiny-talk add-deputy! deputy-object ;; plus
)
(import (rnrs)
(tiny-talk)
(rnrs mutable-pairs (6))
)
;; EXPORTED INTERFACE
;;
;; (start-tiny-talk) -- inits this library!
;; (add-deputy! predicate object) -- add object behaviors to Scheme values
;; (object-deputy value) -> object or #f
;; A Deputy Object is an object deputized to represent a Scheme
;; value type. This allows for methods on Scheme values.
;; A deputy is keyed on a predicate.
;; EXAMPLES:
;; (import (tiny-talk-plus))
;; (start-tiny-talk) ;==> OK
;; (add-deputy! list? (object () [(length self) (length self)] ))
;; (add-deputy! string? (object () [(length self) (string-length self)] ))
;; (add-deputy! vector? (object () [(length self) (vector-length self)] ))
;; [$ length (list 1 2 3) ] ;==> 3
;; [$ length "abc" ] ;==> 3
;; [$ length (vector 1 2 3)] ;==> 3
;;; CAUTION: Predicates should be disjoint! [else order dependent]
;; The function deputy-object takes a Scheme value and
;; returns its deputy object or #f. You can use this to
;; add behaviors.
;; [$ add-method! (deputy-object "a string")
;; 'reverse
;; (lambda (self) (list->string (reverse (string->list self))))]
;; [$ reverse "abc"] ;==> "cba"
;;; CAUTION: shallow-clone and deep-clone only copy a value
;;; there is no cloning of a deputy object.
(define deputy-alist '()) ;; A globle table, sigh.
(define (add-deputy! predicate object)
(unless (and (procedure? predicate)
(object? object))
(error 'add-deputy!
"requires a predicate and an object"
predicate object))
(cond
[(assq predicate deputy-alist)
=>
(lambda (bucket) (set-cdr! bucket object))
]
[else (set! deputy-alist
(cons (cons predicate object) deputy-alist))]
) )
(define (deputy-object thing)
(let loop ( [deps deputy-alist] )
(cond
[(null? deps) #f]
[((caar deps) thing) (cdar deps)]
[else (loop (cdr deps))]
) ) )
(define (deputy-method-finder sym obj)
;; Answer a method or #f
(cond
[(deputy-object obj)
=> ;; object representing a Scheme native type
(lambda (deputy) ([$ lookup deputy] sym))] ; NB: NO delegation
[else #f])
)
(define (start-tiny-talk) ;; ensures this lib is "initialized"
;; Hook into tiny-talk -> (method lookup) function.
(custom-method-finder deputy-method-finder)
'OK)
;; =============================================================
;; Helpers
(define (slice indexed-coll start end repackage)
;; start-inclusive end-exclusive
;; repackage is list-><whatever>
(let loop ( [elts '()] [index (- end 1)] )
(if (< index start)
(repackage elts)
(loop (cons [$ iref indexed-coll index] elts) (- index 1))))
)
(define (id x) x)
;; =============================================================
;; "SIMPLE" (non-collection) OBJECTS
;; name =? shallow-clone deep-clone
(add-deputy! boolean?
(object ()
[(name self) 'boolean]
[(=? self other)
(or (and self other)
(and (not self) (not other)))
]
[(shallow-clone self) (if self #t #f)]
[(deep-clone self) (if self #t #f)]
;; ...
) )
(add-deputy! symbol?
(object ()
[(name self) 'symbol]
[(=? self other) (eq? self other)]
[(shallow-clone self) self]
[(deep-clone self) self]
;; ...
) )
(add-deputy! char?
(object ()
[(name self) 'character]
[(=? self other) (and (char? other)(char=? self other))]
[(shallow-clone self) self]
[(deep-clone self) self]
;; ...
) )
(add-deputy! procedure?
(object ()
[(name self) 'procedure]
[(=? self other) (eq? self other)]
[(shallow-clone self) self]
[(deep-clone self) self]
;; ...
) )
(add-deputy! number?
(object ()
[(name self) 'number]
[(join self other) (+ self other)] ;; test
[(negate self) (- self)]
[(=? self other) (= self other)]
[(shallow-clone self) self]
[(deep-clone self) self]
;; ...
) )
;; =============================================================
;; COLLECTIONS
;; length map for-each every? any? collect reject join
;; iref slice [for indexed collections only]
(add-deputy! string?
(object ()
[(name self) 'string]
[(join self other) (string-append self other)]
[(length self) (string-length self)]
[(iref self index) (string-ref self index)]
[(slice self start end)
;;(slice self start end list->string)
(substring self start end)]
[(=? self other) (and (string? other) (string=? self other))]
[(for-each self proc) ;; for-each-elt
(let ( [limit (string-length self)] )
(let loop ( [index 0] )
(if (>= index limit)
'OK
(begin (proc (string-ref self index))
(loop (+ index 1))))))
]
[(map self proc) ;; NB: returns a string
(let ( [limit (string-length self)] )
(let loop ( [index 0] [results '()] )
(if (>= index limit)
(list->string (reverse results))
(loop (+ index 1)
(cons (proc (string-ref self index))
results)))
) )
]
[(every? self proc) [$ every? (string->list self) proc]]
[(any? self proc) [$ any? (string->list self) proc]]
[(shallow-clone self) (string-copy self)]
[(deep-clone self) (string-copy self)]
[(collect self proc)
(let-values ( [(yes no) (partition proc (string->list self))] )
(list->string yes))]
[(reject self proc)
(let-values ( [(yes no) (partition proc (string->list self))] )
(list->string no))]
;; ...
) )
(add-deputy! vector?
(object ()
[(name self) 'vector]
[(join self other) ;; (vector-append self other)
(unless (vector? other)
(error 'vector:join
"requires two vectors to append together"
self other))
(list->vector
(append (vector->list self)
(vector->list other)))
]
[(=? self other)
(and (vector? other)
(or (eq? self other)
(and (= (vector-length self) (vector-length other))
(call-with-current-continuation
(lambda (return)
(vector-for-each
(lambda (a b)
(unless [$ =? a b] (return #f)))
self other)
(return #t))))))
]
[(length self) (vector-length self)]
[(iref self index) (vector-ref self index)]
[(slice self start end)
(slice self start end list->vector)]
[(for-each self proc) (vector-for-each proc self)]
[(map self proc) (vector-map proc self)]
[(every? self proc) [$ every? (vector->list self) proc]]
[(any? self proc) [$ any? (vector->list self) proc]]
[(shallow-clone self) (vector-map id self)]
[(deep-clone self) (vector-map id self)]
[(collect self proc)
(let-values ( [(yes no) (partition proc (vector->list self))] )
(list->vector yes))]
[(reject self proc)
(let-values ( [(yes no) (partition proc (vector->list self))] )
(list->vector no))]
;; ...
) )
(add-deputy! list?
(object ()
[(name self) 'list]
[(length self) (length self)]
[(join self other) (append self other)]
[(=? self other) (equal? self other)
#| (or (eq? self other)
(and (list? other)
(let loop ( [left self] [right other] )
(cond
[(null? left ) (null? right)]
[(null? right) #f]
[[$ =? (car left) (car right)]
(loop (cdr left) (cdr right))]
[else #f])))) |#
]
[(iref self index) (list-ref self index)]
[(slice self start end)
;; start-inclusive end-exclusive
(let start-loop ( [list self] [index 0] )
(if (< index start)
(start-loop (cdr list) (+ 1 index))
;; ASSERT: (= index start)
(let collect-loop ( [elts '()] [list list] [index index] )
(if (< index end)
(collect-loop (cons (car list) elts)
(cdr list)
(+ index 1))
(reverse elts)))))
]
[(every? self proc) (for-all proc self)]
[(any? self proc) (exists proc self)]
[(shallow-clone self) (map id self)]
[(deep-clone self) (map id self)] ;; bogus
[(for-each self proc) (for-all proc self)]
[(map self proc) (map proc self)]
[(collect self proc)
(let-values ( [(yes no) (partition proc self)] )
yes)]
[(reject self proc)
(let-values ( [(yes no) (partition proc self)] )
no)]
;; ...
) )
)
;; --- E O F --- ;;
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