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guix: utils: Add fold-tree and fold-tree-leaves.

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* guix/utils.scm (fold-tree, fold-tree-leaves): New functions.
* tests/utils.scm: Add tests for them.
This commit is contained in:
Eric Bavier 2014-07-20 11:22:46 -05:00
parent da891830da
commit 516e3b6f7a
2 changed files with 67 additions and 1 deletions
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33
guix/utils.scm
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@ -1,6 +1,7 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2013 Mark H Weaver <mhw@netris.org>
;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
;;;
;;; This file is part of GNU Guix.
;;;
@ -72,6 +73,8 @@
call-with-temporary-output-file
with-atomic-file-output
fold2
fold-tree
fold-tree-leaves
filtered-port
compressed-port
@ -649,6 +652,36 @@ output port, and PROC's result is returned."
(lambda (result1 result2)
(fold2 proc result1 result2 (cdr lst1) (cdr lst2)))))))))
(define (fold-tree proc init children roots)
"Call (PROC NODE RESULT) for each node in the tree that is reachable from
ROOTS, using INIT as the initial value of RESULT. The order in which nodes
are traversed is not specified, however, each node is visited only once, based
on an eq? check. Children of a node to be visited are generated by
calling (CHILDREN NODE), the result of which should be a list of nodes that
are connected to NODE in the tree, or '() or #f if NODE is a leaf node."
(let loop ((result init)
(seen vlist-null)
(lst roots))
(match lst
(() result)
((head . tail)
(if (not (vhash-assq head seen))
(loop (proc head result)
(vhash-consq head #t seen)
(match (children head)
((or () #f) tail)
(children (append tail children))))
(loop result seen tail))))))
(define (fold-tree-leaves proc init children roots)
"Like fold-tree, but call (PROC NODE RESULT) only for leaf nodes."
(fold-tree
(lambda (node result)
(match (children node)
((or () #f) (proc node result))
(else result)))
init children roots))
;;;
;;; Source location.

35
tests/utils.scm
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@ -1,5 +1,6 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
;;;
;;; This file is part of GNU Guix.
;;;
@ -25,7 +26,8 @@
#:use-module (srfi srfi-64)
#:use-module (rnrs bytevectors)
#:use-module (rnrs io ports)
#:use-module (ice-9 match))
#:use-module (ice-9 match)
#:use-module (ice-9 vlist))
(define temp-file
(string-append "t-utils-" (number->string (getpid))))
@ -118,6 +120,37 @@
'(0 1 2 3)))
list))
(let* ((tree (alist->vhash
'((0 2 3) (1 3 4) (2) (3 5 6) (4 6) (5) (6))
hashq))
(add-one (lambda (_ r) (1+ r)))
(tree-lookup (lambda (n) (cdr (vhash-assq n tree)))))
(test-equal "fold-tree, single root"
5 (fold-tree add-one 0 tree-lookup '(0)))
(test-equal "fold-tree, two roots"
7 (fold-tree add-one 0 tree-lookup '(0 1)))
(test-equal "fold-tree, sum"
16 (fold-tree + 0 tree-lookup '(0)))
(test-equal "fold-tree, internal"
18 (fold-tree + 0 tree-lookup '(3 4)))
(test-equal "fold-tree, cons"
'(1 3 4 5 6)
(sort (fold-tree cons '() tree-lookup '(1)) <))
(test-equal "fold-tree, overlapping paths"
'(1 3 4 5 6)
(sort (fold-tree cons '() tree-lookup '(1 4)) <))
(test-equal "fold-tree, cons, two roots"
'(0 2 3 4 5 6)
(sort (fold-tree cons '() tree-lookup '(0 4)) <))
(test-equal "fold-tree-leaves, single root"
2 (fold-tree-leaves add-one 0 tree-lookup '(1)))
(test-equal "fold-tree-leaves, single root, sum"
11 (fold-tree-leaves + 0 tree-lookup '(1)))
(test-equal "fold-tree-leaves, two roots"
3 (fold-tree-leaves add-one 0 tree-lookup '(0 1)))
(test-equal "fold-tree-leaves, two roots, sum"
13 (fold-tree-leaves + 0 tree-lookup '(0 1))))
(test-assert "filtered-port, file"
(let* ((file (search-path %load-path "guix.scm"))
(input (open-file file "r0b")))