SubsetMap¶ Map function over subset and recombine. $ wo 'SubsetMap[Reverse, {a, b, c, d, e}, {2, 4}]' {a, d, c, b, e} The positions may also be given as a span. $ wo 'SubsetMap[Accumulate, {x1, x2, x3, x4, x5, x6}, 2 ;; 5]' {x1, x2, x2 + x3, x2 + x3 + x4, x2 + x3 + x4 + x5, x6}