std::experimental::ranges:: Mergeable

From cppreference.com
template < class I1, class I2, class Out, class R = ranges:: less <> ,

class P1 = ranges:: identity , class P2 = ranges:: identity >
concept bool Mergeable =
InputIterator < I1 > &&
InputIterator < I2 > &&
WeaklyIncrementable < Out > &&
IndirectlyCopyable < I1, Out > &&
IndirectlyCopyable < I2, Out > &&

IndirectStrictWeakOrder < R, ranges :: projected < I1, P1 > , ranges :: projected < I2, P2 >> ;
(ranges TS)

The Mergeable concept specifies the common requirements of algorithms that merge sorted sequences into an output sequence by copying the elements (for example, ranges::merge ).