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;;; Copyright 2024 Masaya Tojo <masaya@tojo.tokyo>
;;;
;;; Licensed under the Apache License, Version 2.0 (the "License");
;;; you may not use this file except in compliance with the License.
;;; You may obtain a copy of the License at
;;;
;;; http://www.apache.org/licenses/LICENSE-2.0
;;;
;;; Unless required by applicable law or agreed to in writing, software
;;; distributed under the License is distributed on an "AS IS" BASIS,
;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;;; See the License for the specific language governing permissions and
;;; limitations under the License.
(define-library (qklib memoization)
(export memoize memoize1)
(import (scheme base)
(scheme case-lambda)
(srfi 128))
(cond-expand
((library (srfi srfi-146 hash)) ; for guile-srfi-146
(import (srfi srfi-146 hash)))
((library (srfi 146 hash))
(import (srfi 146 hash))))
(begin
(define memoize
(case-lambda
((f)
(memoize f (make-default-comparator)))
((f comparator)
(let ((memo (hashmap comparator)))
(let memo-fix ((f f))
(lambda (args)
(hashmap-ref memo args
(lambda ()
(define result (apply (f (memo-fix f)) args))
(set! memo (hashmap-set! memo args result))
result))))))))
(define memoize1
(case-lambda
((f)
(memoize1 f (make-default-comparator)))
((f comparator)
(let ((memo (hashmap comparator)))
(let memo-fix ((f f))
(lambda (x)
(hashmap-ref memo x
(lambda ()
(define result ((f (memo-fix f)) x))
(set! memo (hashmap-set! memo x result))
result))))))))
))
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