MapAt
MapAt allows us to Map a function to specified positions. The next cell maps foo to position 3.
The next cell maps foo to positions {2} and {4}.
Created by Mathematica (May 16, 2004)
![ClearAll["Global`*"] ; MapAt[foo, {a, b, c, d, e, f}, 3]](../HTMLFiles/Tricks_L-O_208.gif){kind=small}
![{a, b, foo[c], d, e, f}](../HTMLFiles/Tricks_L-O_209.gif){kind=small}
![MapAt[foo, {a, b, c, d, e, f}, {{2}, {4}}]](../HTMLFiles/Tricks_L-O_210.gif){kind=small}
![{a, foo[b], c, foo[d], e, f}](../HTMLFiles/Tricks_L-O_211.gif){kind=small}