partition3

auto partition3(alias  less =  "a < b",  SwapStrategy ss =  SwapStrategy.unstable,  Range,  E)(Range r,  E pivot) if (ss ==  SwapStrategy.unstable &&  isRandomAccessRange!Range
        &&  hasSwappableElements!Range &&  hasLength!Range &&  hasSlicing!Range
        &&  is(typeof(binaryFun!less(r.front,  pivot))  ==  bool)
         &&  is(typeof(binaryFun!less(pivot,  r.front))  ==  bool)
         &&  is(typeof(binaryFun!less(r.front,  r.front))  ==  bool))

Rearranges elements in r in three adjacent ranges and returns them.

The first and leftmost range only contains elements in r less than pivot. The second and middle range only contains elements in r that are equal to pivot. Finally, the third and rightmost range only contains elements in r that are greater than pivot. The less-than test is defined by the binary function less.

Parameters

`less`	The predicate to use for the rearrangement.
`ss`	The swapping strategy to use.
`r`	The random-access range to rearrange.
`pivot`	The pivot element.

Returns

A Tuple of the three resulting ranges. These ranges are

slices of the original range.

BUGS: stable partition3 has not been implemented yet.