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Bug 3872: std.algorithm.filter could become bidirectional if its input range is bidir

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This commit is contained in:
David Simcha 2010-07-01 02:24:58 +00:00
parent 947b1cdc7c
commit 96aed784bc
1 changed files with 31 additions and 0 deletions
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31
std/algorithm.d
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@ -565,6 +565,10 @@ struct Filter(alias pred, Range) if (isInputRange!(Range))
{ {
_input = r; _input = r;
while (!_input.empty && !pred(_input.front)) _input.popFront; while (!_input.empty && !pred(_input.front)) _input.popFront;
static if (isBidirectionalRange!Range) {
while (!_input.empty && !pred(_input.back)) _input.popBack;
}
} }
ref Filter opSlice() ref Filter opSlice()
@ -591,6 +595,19 @@ struct Filter(alias pred, Range) if (isInputRange!(Range))
return _input.front; return _input.front;
} }
static if (isBidirectionalRange!Range) {
void popBack()
{
do
{
_input.popBack;
} while (!_input.empty && !pred(_input.back));
}
ElementType!(Range) back() { return _input.back;}
}
static if(isForwardRange!Range) static if(isForwardRange!Range)
{ {
@property typeof(this) save() @property typeof(this) save()
@ -616,10 +633,24 @@ unittest
static assert(isInfinite!(typeof(infinite))); static assert(isInfinite!(typeof(infinite)));
static assert(isForwardRange!(typeof(infinite))); static assert(isForwardRange!(typeof(infinite)));
auto nums = [0,1,2,3,4];
auto forward = filter!"a % 2 == 0"(nums);
assert(equal(retro(forward), [4,2,0][])); // f is a bidirectional range
foreach(DummyType; AllDummyRanges) { foreach(DummyType; AllDummyRanges) {
DummyType d; DummyType d;
auto f = filter!"a & 1"(d); auto f = filter!"a & 1"(d);
assert(equal(f, [1,3,5,7,9])); assert(equal(f, [1,3,5,7,9]));
static if(isForwardRange!DummyType) {
static assert(isForwardRange!(typeof(f)));
}
static if(isBidirectionalRange!DummyType) {
static assert(isBidirectionalRange!(typeof(f)));
assert(equal(retro(f), [9,7,5,3,1]));
}
} }
} }