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Merge pull request #1172 from andralex/5924

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Fixes Issue 5924
This commit is contained in:
Alex Rønne Petersen 2013-02-25 20:28:06 -08:00
commit 707a60101b
1 changed files with 40 additions and 14 deletions
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54
std/algorithm.d
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@ -9056,8 +9056,7 @@ corresponding $(D sort), but $(D schwartzSort) evaluates $(D
transform) only $(D r.length) times (less than half when compared to transform) only $(D r.length) times (less than half when compared to
regular sorting). The usage can be best illustrated with an example. regular sorting). The usage can be best illustrated with an example.
Example: Examples:
---- ----
uint hashFun(string) { ... expensive computation ... } uint hashFun(string) { ... expensive computation ... }
string[] array = ...; string[] array = ...;
@ -9077,24 +9076,51 @@ To check whether an array was sorted and benefit of the speedup of
Schwartz sorting, a function $(D schwartzIsSorted) is not provided Schwartz sorting, a function $(D schwartzIsSorted) is not provided
because the effect can be achieved by calling $(D because the effect can be achieved by calling $(D
isSorted!less(map!transform(r))). isSorted!less(map!transform(r))).
Returns: The initial range wrapped as a $(D SortedRange) with the
predicate $(D (a, b) => binaryFun!less(transform(a),
transform(b))).
*/ */
void schwartzSort(alias transform, alias less = "a < b", SortedRange!(R, ((a, b) => binaryFun!less(transform(a), transform(b))))
SwapStrategy ss = SwapStrategy.unstable, Range)(Range r) schwartzSort(alias transform, alias less = "a < b",
if (isRandomAccessRange!(Range) && hasLength!(Range)) SwapStrategy ss = SwapStrategy.unstable, R)(R r)
if (isRandomAccessRange!R && hasLength!R)
{ {
alias typeof(transform(r.front)) XformType; import core.stdc.stdlib;
auto xform = new XformType[r.length]; alias T = typeof(transform(r.front));
foreach (i, e; r) auto xform1 = (cast(T*) malloc(r.length * T.sizeof))[0 .. r.length];
size_t length;
scope(exit)
{ {
xform[i] = transform(e); static if (hasElaborateDestructor!T)
{
foreach (i; 0 .. length) collectException(destroy(xform1[i]));
}
free(xform1.ptr);
} }
auto z = zip(xform, r); for (; length != r.length; ++length)
alias typeof(z.front) ProxyType;
bool myLess(ProxyType a, ProxyType b)
{ {
return binaryFun!less(a[0], b[0]); emplace(xform1.ptr + length, transform(r[length]));
} }
sort!(myLess, ss)(z); // Make sure we use ubyte[] and ushort[], not char[] and wchar[]
// for the intermediate array, lest zip gets confused.
static if (isNarrowString!(typeof(xform1)))
{
auto xform = xform1.representation();
}
else
{
alias xform = xform1;
}
zip(xform, r).sort!((a, b) => binaryFun!less(a[0], b[0]), ss)();
return typeof(return)(r);
}
unittest
{
// issue 5924
Tuple!(char)[] chars;
schwartzSort!((Tuple!(char) c){ return c[0]; })(chars);
} }
unittest unittest