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Util: fix binary search exit condition

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The loop can exit with an interval of length one or one of
length zero. In the first case it is correct to check which side
of the interval to return, in the second case no comparison should
be made (since there is only one possible value).
In practice, this usually results in one comparison more than needed,
but in some cases (when the position was past the end of the array),
would call the comparator with undefined.

https://bugzilla.gnome.org/show_bug.cgi?id=666614
This commit is contained in:
Giovanni Campagna 2011-12-20 21:30:30 +01:00
parent 087d8e602e
commit bbdce159fa
2 changed files with 7 additions and 2 deletions
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2
js/misc/util.js
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@ -265,7 +265,7 @@ function lowerBound(array, val, cmp) {
max = mid; max = mid;
} }
return (cmp(array[min], val) < 0) ? max : min; return (min == max || cmp(array[min], val) < 0) ? max : min;
} }
// insertSorted: // insertSorted:

7
tests/unit/insertSorted.js
View File

@ -64,8 +64,13 @@ let arrayEmpty = [];
// inserting in a empty array // inserting in a empty array
Util.insertSorted(arrayEmpty, 3, checkedCmp); Util.insertSorted(arrayEmpty, 3, checkedCmp);
// Insert at the end and check that we don't
// access past it
Util.insertSorted(arrayEmpty, 4, checkedCmp);
Util.insertSorted(arrayEmpty, 5, checkedCmp);
// Some more insertions // Some more insertions
Util.insertSorted(arrayEmpty, 2, checkedCmp); Util.insertSorted(arrayEmpty, 2, checkedCmp);
Util.insertSorted(arrayEmpty, 1, checkedCmp); Util.insertSorted(arrayEmpty, 1, checkedCmp);
assertArrayEquals('checkedCmp test', [1, 2, 3], arrayEmpty); assertArrayEquals('checkedCmp test', [1, 2, 3, 4, 5], arrayEmpty);