https://issues.dlang.org/show_bug.cgi?id=15421
Issue ID: 15421
Summary: The behaviours of the topNs differ with the bottom
Product: D
Version: D2
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P1
Component: phobos
Assignee: [email protected]
Reporter: [email protected]
============
import std.algorithm;
void main() {
auto a = [ 9, 8, 0, 3, 5, 25, 43, 4, 2, 0, 7 ];
auto b = [ 9, 8, 0, 3, 5, 25, 43, 4, 2, 0, 7 ];
topN(a, 4);
topN(b[0 .. 4], b[4 .. $]);
sort(a[0 .. 4]); sort(a[4 .. $]);
sort(b[0 .. 4]); sort(b[4 .. $]);
assert(a[0 .. 4] == b[0 .. 4]);
assert(a[4 .. $] == b[4 .. $]); // This one fails
assert(a == b); // As would this one obviously
}
============
Basically, topN(Range, index) rearranges *all* of the elements such that all
those on the left are smaller (or whatever the predicate specifies) than those
on the right, while still keeping all the elements. However, topN(Range,
Range) leaves the second range untouched such that you end up with with some
elements disappearing and others being duplicated.
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