This is documentation for Mathematica 5, which was
based on an earlier version of the Wolfram Language.

 ReplacePart ReplacePart[expr, new, n] yields an expression in which the n part of expr is replaced by new. ReplacePart[expr, new, i, j, ... ] replaces the part at position i, j, ... . ReplacePart[expr, new, , , ... , , , ... , ... ] replaces parts at several positions by new. ReplacePart[expr, new, pos, npos] replaces parts at positions pos in expr by parts at positions npos in new. Example: ReplacePart[a, b, c, d, x, 3] . The list of positions used by ReplacePart is in the same form as is returned by the function Position. ReplacePart[expr, Hold[new], pos, 1] can be used to replace a part without evaluating it. If pos and npos both specify multiple parts, each part in pos is replaced by the corresponding part in npos. ReplacePart can be used on SparseArray objects. See Section 1.8.6, Section 2.1.4, Section 2.1.4 and Section 2.4.2. See also: Part, Extract, MapAt, FlattenAt, Insert, Delete, Sequence, StringReplacePart. New in Version 2; modified in 3.