26 Numerics library [numerics]

26.6 Numeric arrays [numarray]

26.6.8 Class template mask_array [template.mask.array]

26.6.8.4 mask_array fill function [mask.array.fill]

void operator=(const T&) const;

This function has reference semantics, assigning the value of its argument to the elements of the valarray<T> object to which the mask_array object refers.