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-rw-r--r--module/rnrs/base.scm72
1 files changed, 71 insertions, 1 deletions
diff --git a/module/rnrs/base.scm b/module/rnrs/base.scm
index 4cfd1d1cc..499a22444 100644
--- a/module/rnrs/base.scm
+++ b/module/rnrs/base.scm
@@ -73,7 +73,7 @@
let-syntax letrec-syntax
syntax-rules identifier-syntax)
- (import (rename (except (guile) error raise)
+ (import (rename (except (guile) error raise map)
(log log-internal)
(euclidean-quotient div)
(euclidean-remainder mod)
@@ -86,6 +86,76 @@
(inexact->exact exact))
(srfi srfi-11))
+ (define map
+ (case-lambda
+ ((f l)
+ (let map1 ((hare l) (tortoise l) (move? #f) (out '()))
+ (if (pair? hare)
+ (if move?
+ (if (eq? tortoise hare)
+ (scm-error 'wrong-type-arg "map" "Circular list: ~S"
+ (list l) #f)
+ (map1 (cdr hare) (cdr tortoise) #f
+ (cons (f (car hare)) out)))
+ (map1 (cdr hare) tortoise #t
+ (cons (f (car hare)) out)))
+ (if (null? hare)
+ (reverse out)
+ (scm-error 'wrong-type-arg "map" "Not a list: ~S"
+ (list l) #f)))))
+
+ ((f l1 l2)
+ (let map2 ((h1 l1) (h2 l2) (t1 l1) (t2 l2) (move? #f) (out '()))
+ (cond
+ ((pair? h1)
+ (cond
+ ((not (pair? h2))
+ (scm-error 'wrong-type-arg "map"
+ (if (list? h2)
+ "List of wrong length: ~S"
+ "Not a list: ~S")
+ (list l2) #f))
+ ((not move?)
+ (map2 (cdr h1) (cdr h2) t1 t2 #t
+ (cons (f (car h1) (car h2)) out)))
+ ((eq? t1 h1)
+ (scm-error 'wrong-type-arg "map" "Circular list: ~S"
+ (list l1) #f))
+ ((eq? t2 h2)
+ (scm-error 'wrong-type-arg "map" "Circular list: ~S"
+ (list l2) #f))
+ (else
+ (map2 (cdr h1) (cdr h2) (cdr t1) (cdr t2) #f
+ (cons (f (car h1) (car h2)) out)))))
+
+ ((and (null? h1) (null? h2))
+ (reverse out))
+
+ ((null? h1)
+ (scm-error 'wrong-type-arg "map"
+ (if (list? h2)
+ "List of wrong length: ~S"
+ "Not a list: ~S")
+ (list l2) #f))
+ (else
+ (scm-error 'wrong-type-arg "map"
+ "Not a list: ~S"
+ (list l1) #f)))))
+
+ ((f l1 . rest)
+ (let ((len (length l1)))
+ (let mapn ((rest rest))
+ (or (null? rest)
+ (if (= (length (car rest)) len)
+ (mapn (cdr rest))
+ (scm-error 'wrong-type-arg "map" "List of wrong length: ~S"
+ (list (car rest)) #f)))))
+ (let mapn ((l1 l1) (rest rest) (out '()))
+ (if (null? l1)
+ (reverse out)
+ (mapn (cdr l1) (map cdr rest)
+ (cons (apply f (car l1) (map car rest)) out)))))))
+
(define log
(case-lambda
((n)