Function gfor

test/histogram.cpp:238–238

    array B   = constant(0, 100, 1, 3);

    gfor(seq ii, 3) { B(span, span, ii) = histogram(A(span, span, ii), 100); }

    for (int ii = 0; ii < 3; ii++) {
        array c_ii = histogram(A(span, span, ii), 100);