MapAt

MapAt[f, expr, n] applies f to the element at position n in expr. If n is negative, the position is counted from the end.

MapAt[f, expr, i, j, ... ] applies f to the part of expr at position i, j, ... .

MapAt[f, expr, , , ... , , , ... , ... ] applies f to parts of expr at several positions.

Example: MapAt[f, a, b, c, 2] .

MapAt[f, a, b, c, d, 1, 4] .

MapAt[f, expr, i, j, ... ] or MapAt[f, expr, i, j, ... ] applies f to the part expr[[i, j, ... ]].

MapAt[f, expr, , , ... , , , ... , ... ] applies f to parts expr[[, , ... ]], expr[[, , ... ]], ... .

The list of positions used by MapAt is in the same form as is returned by the function Position.

MapAt applies f repeatedly to a particular part if that part is mentioned more than once in the list of positions.

Example: MapAt[f, a, b, c, 1, 3, 1] .

See The Mathematica Book: Section 2.2.4.

See also: ReplacePart, Delete, FlattenAt.

Further Examples