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Rewrite boot-9 map to be recursive and pure
* module/ice-9/boot-9.scm (map): Rewrite to be recursive and pure instead of iterative and effectful. At best this is faster; at worst it is slower. In any case it resolves continuation-related issues. * module/srfi/srfi-1.scm (fold): Specialize the two-arg case. (map): Rewrite to be recursive. * test-suite/tests/r5rs_pitfall.test (8.3): Update for new expected map behavior.
This commit is contained in:
Andy Wingo
parent
de0233af17
commit
9de674e6e6
3 changed files with 98 additions and 121 deletions
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@ -239,49 +239,83 @@ file with the given name already exists, the effect is unspecified."
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;;; Boot versions of `map' and `for-each', enough to get the expander
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;;; running.
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;;; {map and for-each}
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;;;
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(define map
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(case-lambda
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((f l)
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(if (not (list? l))
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(scm-error 'wrong-type-arg "map" "Not a list: ~S"
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(list l) #f))
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(let map1 ((l l))
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(if (null? l)
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'()
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(cons (f (car l)) (map1 (cdr l))))))
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(if (pair? l)
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(cons (f (car l)) (map1 (cdr l)))
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'())))
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((f l1 l2)
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(if (not (= (length l1) (length l2)))
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(scm-error 'wrong-type-arg "map" "List of wrong length: ~S"
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(list l2) #f))
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(let map2 ((l1 l1) (l2 l2))
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(if (null? l1)
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'()
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(if (pair? l1)
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(cons (f (car l1) (car l2))
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(map2 (cdr l1) (cdr l2))))))
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(map2 (cdr l1) (cdr l2)))
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'())))
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((f l1 . rest)
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(let lp ((l1 l1) (rest rest))
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(if (null? l1)
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'()
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(let ((len (length l1)))
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(let mapn ((rest rest))
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(or (null? rest)
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(if (= (length (car rest)) len)
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(mapn (cdr rest))
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(scm-error 'wrong-type-arg "map" "List of wrong length: ~S"
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(list (car rest)) #f)))))
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(let mapn ((l1 l1) (rest rest))
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(if (pair? l1)
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(cons (apply f (car l1) (map car rest))
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(lp (cdr l1) (map cdr rest))))))))
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(mapn (cdr l1) (map cdr rest)))
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'())))))
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(define map-in-order map)
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(define for-each
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(case-lambda
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((f l)
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(if (not (list? l))
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(scm-error 'wrong-type-arg "for-each" "Not a list: ~S" (list l) #f))
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(let for-each1 ((l l))
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(if (pair? l)
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(if (not (null? l))
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(begin
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(f (car l))
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(for-each1 (cdr l))))))
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((f l1 l2)
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(if (not (= (length l1) (length l2)))
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(scm-error 'wrong-type-arg "for-each" "List of wrong length: ~S"
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(list l2) #f))
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(let for-each2 ((l1 l1) (l2 l2))
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(if (pair? l1)
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(if (not (null? l1))
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(begin
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(f (car l1) (car l2))
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(for-each2 (cdr l1) (cdr l2))))))
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((f l1 . rest)
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(let lp ((l1 l1) (rest rest))
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(let ((len (length l1)))
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(let for-eachn ((rest rest))
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(or (null? rest)
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(if (= (length (car rest)) len)
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(for-eachn (cdr rest))
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(scm-error 'wrong-type-arg "for-each" "List of wrong length: ~S"
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(list (car rest)) #f)))))
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(let for-eachn ((l1 l1) (rest rest))
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(if (pair? l1)
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(begin
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(apply f (car l1) (map car rest))
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(lp (cdr l1) (map cdr rest))))))))
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(for-eachn (cdr l1) (map cdr rest))))))))
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;; Temporary definition used in the include-from-path expansion;
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;; replaced later.
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@ -829,83 +863,6 @@ for key @var{k}, then invoke @var{thunk}."
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(define! 'throw throw))
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;;; The real versions of `map' and `for-each', with cycle detection, and
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;;; that use reverse! instead of recursion in the case of `map'.
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;;;
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(define map
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(case-lambda
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((f l)
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(unless (list? l)
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(scm-error 'wrong-type-arg "map" "Not a list: ~S"
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(list l) #f))
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(let map1 ((l l) (out '()))
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(if (pair? l)
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(map1 (cdr l) (cons (f (car l)) out))
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(reverse! out))))
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((f l1 l2)
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(unless (= (length l1) (length l2))
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(scm-error 'wrong-type-arg "map" "List of wrong length: ~S"
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(list l2) #f))
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(let map2 ((l1 l1) (l2 l2) (out '()))
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(if (pair? l1)
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(map2 (cdr l1) (cdr l2) (cons (f (car l1) (car l2)) out))
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(reverse! out))))
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((f l1 . rest)
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(let ((len (length l1)))
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(let mapn ((rest rest))
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(or (null? rest)
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(if (= (length (car rest)) len)
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(mapn (cdr rest))
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(scm-error 'wrong-type-arg "map" "List of wrong length: ~S"
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(list (car rest)) #f)))))
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(let mapn ((l1 l1) (rest rest) (out '()))
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(if (null? l1)
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(reverse! out)
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(mapn (cdr l1) (map cdr rest)
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(cons (apply f (car l1) (map car rest)) out)))))))
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(define map-in-order map)
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(define for-each
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(case-lambda
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((f l)
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(unless (list? l)
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(scm-error 'wrong-type-arg "for-each" "Not a list: ~S" (list l) #f))
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(let for-each1 ((l l))
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(unless (null? l)
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(f (car l))
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(for-each1 (cdr l)))))
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((f l1 l2)
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(unless (= (length l1) (length l2))
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(scm-error 'wrong-type-arg "for-each" "List of wrong length: ~S"
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(list l2) #f))
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(let for-each2 ((l1 l1) (l2 l2))
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(unless (null? l1)
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(f (car l1) (car l2))
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(for-each2 (cdr l1) (cdr l2)))))
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((f l1 . rest)
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(let ((len (length l1)))
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(let for-eachn ((rest rest))
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(or (null? rest)
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(if (= (length (car rest)) len)
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(for-eachn (cdr rest))
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(scm-error 'wrong-type-arg "for-each" "List of wrong length: ~S"
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(list (car rest)) #f)))))
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(let for-eachn ((l1 l1) (rest rest))
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(if (pair? l1)
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(begin
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(apply f (car l1) (map car rest))
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(for-eachn (cdr l1) (map cdr rest))))))))
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;;;
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@ -454,21 +454,41 @@ a list of those after."
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;;; Fold, unfold & map
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(define (fold kons knil list1 . rest)
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"Apply PROC to the elements of LIST1 ... LISTN to build a result, and return
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(define fold
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(case-lambda
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"Apply PROC to the elements of LIST1 ... LISTN to build a result, and return
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that result. See the manual for details."
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(check-arg procedure? kons fold)
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(if (null? rest)
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(let f ((knil knil) (list1 list1))
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(if (null? list1)
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knil
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(f (kons (car list1) knil) (cdr list1))))
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(let f ((knil knil) (lists (cons list1 rest)))
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(if (any null? lists)
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knil
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(let ((cars (map car lists))
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(cdrs (map cdr lists)))
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(f (apply kons (append! cars (list knil))) cdrs))))))
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((kons knil list1)
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(check-arg procedure? kons fold)
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(check-arg list? list1 fold)
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(let fold1 ((knil knil) (list1 list1))
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(if (pair? list1)
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(fold1 (kons (car list1) knil) (cdr list1))
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knil)))
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((kons knil list1 list2)
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(check-arg procedure? kons fold)
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(let* ((len1 (length+ list1))
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(len2 (length+ list2))
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(len (if (and len1 len2)
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(min len1 len2)
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(or len1 len2))))
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(unless len
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(scm-error 'wrong-type-arg "fold"
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"Args do not contain a proper (finite) list: ~S"
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(list (list list1 list2)) #f))
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(let fold2 ((knil knil) (list1 list1) (list2 list2) (len len))
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(if (zero? len)
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knil
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(fold2 (kons (car list1) (car list2) knil)
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(cdr list1) (cdr list2) (1- len))))))
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((kons knil list1 . rest)
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(check-arg procedure? kons fold)
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(let foldn ((knil knil) (lists (cons list1 rest)))
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(if (any null? lists)
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knil
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(let ((cars (map car lists))
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(cdrs (map cdr lists)))
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(foldn (apply kons (append! cars (list knil))) cdrs)))))))
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(define (fold-right kons knil clist1 . rest)
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(check-arg procedure? kons fold-right)
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@ -567,10 +587,10 @@ has just one element then that's the return value."
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((f l)
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(check-arg procedure? f map)
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(check-arg list? l map)
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(let map1 ((in l) (out '()))
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(if (pair? in)
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(map1 (cdr in) (cons (f (car in)) out))
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(reverse! out))))
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(let map1 ((l l))
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(if (pair? l)
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(cons (f (car l)) (map1 (cdr l)))
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'())))
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((f l1 l2)
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(check-arg procedure? f map)
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@ -583,11 +603,11 @@ has just one element then that's the return value."
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(scm-error 'wrong-type-arg "map"
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"Args do not contain a proper (finite) list: ~S"
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(list (list l1 l2)) #f))
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(let map2 ((l1 l1) (l2 l2) (out '()) (len len))
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(let map2 ((l1 l1) (l2 l2) (len len))
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(if (zero? len)
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(reverse! out)
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(map2 (cdr l1) (cdr l2)
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(cons (f (car l1) (car l2)) out) (1- len))))))
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'()
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(cons (f (car l1) (car l2))
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(map2 (cdr l1) (cdr l2) (1- len)))))))
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((f l1 . rest)
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(check-arg procedure? f map)
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@ -602,11 +622,11 @@ has just one element then that's the return value."
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(scm-error 'wrong-type-arg "map"
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"Args do not contain a proper (finite) list: ~S"
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(list (cons l1 rest)) #f))
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(let mapn ((l1 l1) (rest rest) (len len) (out '()))
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(let mapn ((l1 l1) (rest rest) (len len))
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(if (zero? len)
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(reverse! out)
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(mapn (cdr l1) (map cdr rest) (1- len)
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(cons (apply f (car l1) (map car rest)) out))))))))
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'()
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(cons (apply f (car l1) (map car rest))
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(mapn (cdr l1) (map cdr rest) (1- len)))))))))
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(define map-in-order map)
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@ -1,5 +1,5 @@
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;;;; r5rs_pitfall.test --- tests some pitfalls in R5RS -*- scheme -*-
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;;;; Copyright (C) 2003, 2004, 2006 Free Software Foundation, Inc.
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;;;; Copyright (C) 2003, 2004, 2006, 2014 Free Software Foundation, Inc.
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;;;;
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;;;; This library is free software; you can redistribute it and/or
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;;;; modify it under the terms of the GNU Lesser General Public
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@ -292,7 +292,7 @@
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;;Not really an error to fail this (Matthias Radestock)
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;;If this returns (0 1 0), your map isn't call/cc safe, but is probably
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;;tail-recursive. If its (0 0 0), the opposite is true.
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(should-be 8.3 '(0 1 0)
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(should-be 8.3 '(0 0 0)
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(let ()
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(define executed-k #f)
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(define cont #f)
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