Sean Kelly wrote:
== Quote from Andrei Alexandrescu ([email protected])'s article
Sean Kelly wrote:
Andrei Alexandrescu wrote:
Note how the left edge of result follows the left edge of r, but the
right edge stays put because partition() returns the right-hand-side
range. r shrinks from both ends to exhaustion.
So all the elements that satisfy the predicate end up at the end of the
original range instead of the beginning? Was that an arbitrary choice,
or is there a reason for it?
The elements satisfying the predicate are at the beginning, see e.g. the
unittests. The range returned is (as always) the right-hand side, i.e.
the range containing the elements that don't satisfy the predicate.
Weird. I'd always thought that the standard behavior was the opposite.
That way partition could be passed a lessThan predicate and be used
for sorting. Though I guess you can just use a greaterThan predicate
instead.
Nono, lessThan is a binary predicate whereas partition takes a unary
predicate. The spec of partition is very simple: do whatever the hell it
takes to put elements e that satisfy pred(e) before elements that don't.
If you follow the way std.sort uses partition, you'll see that it passes
a unary predicate that compares for less than against the chosen pivot.
Andrei
