This is documentation for Mathematica 6, which was
based on an earlier version of the Wolfram Language.

# 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, {{i1, j1, ...}, {i2, j2, ...}, ...}]applies f to parts of expr at several positions.
• MapAt[f, expr, {i, j, ...}] or MapAt[f, expr, {{i, j, ...}}] applies f to the part expr[[i, j, ...]].
• MapAt[f, expr, {{i1, j1, ...}, {i2, j2, ...}, ...}] applies f to parts expr[[i1, j1, ...]], expr[[i2, j2, ...]], ....  »
• 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.  »
Map f onto the part at position 2:
 Out[1]=

Map f onto multiple parts:
 Out[1]=

Map f onto a more deeply nested part:
 Out[1]=
 Scope   (5)
 Applications   (4)
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