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[Issue 16170] Seperate std.algorithm.sorting.partition into various overloads in order to facilitate further improvements

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This commit is contained in:
Jack Stouffer 2016-07-31 14:10:02 -04:00
parent e15e7c08a5
commit e21f2729ba
1 changed files with 28 additions and 20 deletions
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48
std/algorithm/sorting.d
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@ -385,31 +385,38 @@ See_Also:
STL's $(HTTP sgi.com/tech/stl/_partition.html, _partition)$(BR) STL's $(HTTP sgi.com/tech/stl/_partition.html, _partition)$(BR)
STL's $(HTTP sgi.com/tech/stl/stable_partition.html, stable_partition) STL's $(HTTP sgi.com/tech/stl/stable_partition.html, stable_partition)
*/ */
Range partition(alias predicate, Range partition(alias predicate, SwapStrategy ss, Range)(Range r)
SwapStrategy ss = SwapStrategy.unstable, Range)(Range r) if (ss == SwapStrategy.stable && isRandomAccessRange!(Range) && hasLength!Range && hasSlicing!Range)
if ((ss == SwapStrategy.stable && isRandomAccessRange!(Range) && hasLength!Range && hasSlicing!Range)
|| (ss != SwapStrategy.stable && isForwardRange!(Range)))
{ {
import std.algorithm.mutation : bringToFront;
alias pred = unaryFun!(predicate); alias pred = unaryFun!(predicate);
if (r.empty) return r; if (r.empty) return r;
static if (ss == SwapStrategy.stable)
if (r.length == 1)
{ {
import std.algorithm.mutation : bringToFront; if (pred(r.front)) r.popFront();
if (r.length == 1) return r;
{
if (pred(r.front)) r.popFront();
return r;
}
const middle = r.length / 2;
alias recurse = .partition!(pred, ss, Range);
auto lower = recurse(r[0 .. middle]);
auto upper = recurse(r[middle .. r.length]);
bringToFront(lower, r[middle .. r.length - upper.length]);
return r[r.length - lower.length - upper.length .. r.length];
} }
else static if (ss == SwapStrategy.semistable) const middle = r.length / 2;
alias recurse = .partition!(pred, ss, Range);
auto lower = recurse(r[0 .. middle]);
auto upper = recurse(r[middle .. r.length]);
bringToFront(lower, r[middle .. r.length - upper.length]);
return r[r.length - lower.length - upper.length .. r.length];
}
///ditto
Range partition(alias predicate, SwapStrategy ss = SwapStrategy.unstable, Range)(Range r)
if (ss != SwapStrategy.stable && isInputRange!Range && hasSwappableElements!Range)
{
import std.algorithm.mutation : swap;
alias pred = unaryFun!(predicate);
static if (ss == SwapStrategy.semistable)
{ {
import std.algorithm.mutation : swap; if (r.empty) return r;
for (; !r.empty; r.popFront()) for (; !r.empty; r.popFront())
{ {
// skip the initial portion of "correct" elements // skip the initial portion of "correct" elements
@ -424,9 +431,10 @@ Range partition(alias predicate,
} }
return result; return result;
} }
return r; return r;
} }
else // ss == SwapStrategy.unstable else
{ {
// Inspired from www.stepanovpapers.com/PAM3-partition_notes.pdf, // Inspired from www.stepanovpapers.com/PAM3-partition_notes.pdf,
// section "Bidirectional Partition Algorithm (Hoare)" // section "Bidirectional Partition Algorithm (Hoare)"