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take(take(range,...),n) is take(range, n) and use slicing in take like in takeExactly

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Also take!R is the same as takeExactly!R when isInfinite!R.
This commit is contained in:
Nathan Sashihara 2018-11-05 17:18:14 -05:00
parent 184d307e40
commit 6b22cd60df
1 changed files with 50 additions and 23 deletions
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65
source/tanya/algorithm/iteration.d
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@ -24,7 +24,7 @@ import tanya.algorithm.comparison;
import tanya.algorithm.mutation;
import tanya.range;
private mixin template Take(R, bool exactly)
private struct Take(R, bool exactly)
{
private R source;
size_t length_;
@ -187,6 +187,22 @@ private mixin template Take(R, bool exactly)
}
}
}
static if (!exactly && hasSlicing!R)
{
auto opSlice(size_t i, size_t j)
in
{
assert(i <= j);
assert(j <= length);
}
do
{
return typeof(this)(this.source[i .. j], length);
}
}
version (unittest) static assert(isInputRange!Take);
}
/**
@ -212,26 +228,35 @@ private mixin template Take(R, bool exactly)
auto take(R)(R range, size_t n)
if (isInputRange!R)
{
static struct Take
static if (hasSlicing!R && hasLength!R)
{
mixin .Take!(R, false);
static if (hasSlicing!R)
if (range.length <= n)
return range;
else
return range[0 .. n];
}
// Special case: take(take(...), n)
else static if (is(Range == Take!(RRange, exact), RRange, bool exact))
{
auto opSlice(size_t i, size_t j)
in
if (n > range.length_)
n = range.length_;
static if (exact)
// `take(takeExactly(r, n0), n)` is rewritten `takeExactly(r, min(n0, n))`.
return Take!(RRange, true)(range.source, n);
else
// `take(take(r, n0), n)` is rewritten `take(r, min(n0, n))`.
return Take!(RRange, false)(range.source, n);
}
else static if (isInfinite!R)
{
assert(i <= j);
assert(j <= length);
// If the range is infinite then `take` is the same as `takeExactly`.
return Take!(R, true)(range, n);
}
do
else
{
return typeof(this)(this.source[i .. j], length);
return Take!(R, false)(range, n);
}
}
}
return Take(range, n);
}
///
@nogc nothrow pure @safe unittest
@ -315,13 +340,15 @@ if (isInputRange!R)
{
return range[0 .. n];
}
// Special case: takeExactly(take(range, ...), n) is takeExactly(range, n)
else static if (is(Range == Take!(RRange, exact), RRange, bool exact))
{
assert(n <= range.length_);
return Take!(RRange, true)(range.source, n);
}
else
{
static struct TakeExactly
{
mixin Take!(R, true);
}
return TakeExactly(range, n);
return Take!(R, true)(range, n);
}
}