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Add intmap-prev

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* module/language/cps/intmap.scm (intmap-next): Starting index is
  optional.
  (intmap-prev): New function.
This commit is contained in:
Andy Wingo 2015-03-27 10:34:40 +01:00
parent 33ab2838de
commit 2a24395a0f
1 changed files with 22 additions and 1 deletions
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23
module/language/cps/intmap.scm
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@ -39,6 +39,7 @@
intmap-remove
intmap-ref
intmap-next
intmap-prev
intmap-union
intmap-intersect))
@ -191,7 +192,7 @@
*branch-mask*)))
(lp (vector-ref node idx) shift)))))))))))
(define (intmap-next bs i)
(define* (intmap-next bs #:optional i)
(define (visit-branch node shift i)
(let lp ((i i) (idx (logand (ash i (- shift)) *branch-mask*)))
(and (< idx *branch-size*)
@ -212,6 +213,26 @@
(let ((i (visit-node root shift i)))
(and i (+ min i))))))))
(define* (intmap-prev bs #:optional i)
(define (visit-branch node shift i)
(let lp ((i i) (idx (logand (ash i (- shift)) *branch-mask*)))
(and (<= 0 idx)
(or (visit-node (vector-ref node idx) shift i)
(lp (1- (round-down i shift)) (1- idx))))))
(define (visit-node node shift i)
(and node
(if (zero? shift)
i
(visit-branch node (- shift *branch-bits*) i))))
(match bs
(($ <intmap> min shift root)
(let* ((i (if (and i (< i (+ min (ash 1 shift))))
(- i min)
(1- (ash 1 shift)))))
(and (<= 0 i)
(let ((i (visit-node root shift i)))
(and i (+ min i))))))))
(define* (intmap-union a b #:optional (meet meet-error))
;; Union A and B from index I; the result will be fresh.
(define (union-branches/fresh shift a b i fresh)