From 274df27f641a0df9b26ac0537119b149fa0ba7d1 Mon Sep 17 00:00:00 2001
From: Masaya Tojo <masaya@tojo.tokyo>
Date: Thu, 22 Aug 2024 03:34:40 +0900
Subject: Initial commit

---
 integer-partition/accel-asc.scm | 62 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 integer-partition/accel-asc.scm

(limited to 'integer-partition')

diff --git a/integer-partition/accel-asc.scm b/integer-partition/accel-asc.scm
new file mode 100644
index 0000000..6b44e4d
--- /dev/null
+++ b/integer-partition/accel-asc.scm
@@ -0,0 +1,62 @@
+;;; 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 (integer-partition accel-asc)
+  (export accel-asc)
+  (import (scheme base))
+  (cond-expand
+    ((library (scheme generator))
+     (import (only (scheme generator) make-coroutine-generator)))
+    ((library (srfi 158))
+     (import (only (srfi 158) make-coroutine-generator))))
+  (begin
+    (define-syntax while
+      (syntax-rules ()
+        ((_ condition body body* ...)
+         (let loop ()
+           (if condition
+               (begin
+                 body
+                 body* ...
+                 (loop))
+               (if #f #f)))))))
+  (begin
+    (define (accel-asc n)
+      (accel-asc* n vector->list))
+
+    (define (accel-asc* n convert)
+      (make-coroutine-generator
+       (lambda (yield)
+         (let ((a (make-vector (+ n 1) 0))
+               (k 1)
+               (x 0)
+               (y (- n 1)))
+           (while (not (= k 0))
+             (set! x (+ (vector-ref a (- k 1)) 1))
+             (set! k (- k 1))
+             (while (<= (* 2 x) y)
+               (vector-set! a k x)
+               (set! y (- y x))
+               (set! k (+ k 1)))
+             (let ((l (+ k 1)))
+               (while (<= x y)
+                 (vector-set! a k x)
+                 (vector-set! a l y)
+                 (yield (convert a 0 (+ k 2)))
+                 (set! x (+ x 1))
+                 (set! y (- y 1)))
+               (vector-set! a k (+ x y))
+               (set! y (+ x y -1))
+               (yield (convert a 0 (+ k 1)))))))))
+    ))
-- 
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