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Fix Issue 8472 - Replace walkLength() with an improved count() #5545

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Fix Issue 8472 - Replace walkLength() with an improved count() #5545

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58eba76
Fix Issue 8472 - Replace walkLength() with an improved count()
RazvanN7 Jul 5, 2017
062948f
Fix documentation and add overload
RazvanN7 Jul 5, 2017
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12 changes: 11 additions & 1 deletion std/algorithm/searching.d
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Original file line number Diff line number Diff line change
Expand Up @@ -692,7 +692,7 @@ if (isForwardRange!R1 && !isInfinite!R1 &&
}

/// Ditto
size_t count(alias pred = "true", R)(R haystack)
size_t count(alias pred, R)(R haystack)
if (isInputRange!R && !isInfinite!R &&
is(typeof(unaryFun!pred(haystack.front)) : bool))
{
Expand All @@ -703,6 +703,16 @@ if (isInputRange!R && !isInfinite!R &&
return result;
}

/// Ditto
size_t count(R)(R haystack)
if (isInputRange!R && !isInfinite!R)
{
static if (hasLength!R)
return haystack.length;
else
return count!"true"(haystack);
}

@safe unittest
{
int[] a = [ 1, 2, 4, 3, 2, 5, 3, 2, 4 ];
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31 changes: 15 additions & 16 deletions std/range/primitives.d
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Original file line number Diff line number Diff line change
Expand Up @@ -1625,44 +1625,43 @@ range.
If $(D hasLength!Range), simply returns $(D range.length) without
checking $(D upTo) (when specified).

Otherwise, walks the range through its length and returns the number
of elements seen. Performes $(BIGOH n) evaluations of $(D range.empty)
Otherwise, walks the range for $(D upTo) elements. If $(D range.length) is smaller
than $(D upTo), the walking stops returning $(D range.length).

Performes $(BIGOH n) evaluations of $(D range.empty)
and $(D range.popFront()), where $(D n) is the effective length of $(D
range).

The $(D upTo) parameter is useful to "cut the losses" in case
the interest is in seeing whether the range has at least some number
of elements. If the parameter $(D upTo) is specified, stops if $(D
upTo) steps have been taken and returns $(D upTo).

Infinite ranges are compatible, provided the parameter $(D upTo) is
specified, in which case the implementation simply returns upTo.
*/
auto walkLength(Range)(Range range)
if (isInputRange!Range && !isInfinite!Range)
auto walkLength(Range)(Range range, const size_t upTo)
if (isInputRange!Range)
{
static if (hasLength!Range)
return range.length;
else static if (isInfinite!Range)
return upTo;
else
{
size_t result;
for ( ; !range.empty ; range.popFront() )
for ( ; result < upTo && !range.empty ; range.popFront() )
++result;
return result;
}
}
/// ditto
auto walkLength(Range)(Range range, const size_t upTo)
if (isInputRange!Range)

//@@@DEPRECATED_2018-07@@@
deprecated("use std.algorithm.searching.count instead.")
auto walkLength(Range)(Range range)
if (isInputRange!Range && !isInfinite!Range)
{
static if (hasLength!Range)
return range.length;
else static if (isInfinite!Range)
return upTo;
else
{
size_t result;
for ( ; result < upTo && !range.empty ; range.popFront() )
for ( ; !range.empty ; range.popFront() )
++result;
return result;
}
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