Position

Usage

• Position[expr, pattern] gives a list of the positions at which objects matching pattern appear in expr.
• Position[expr, pattern, levspec] finds only objects that appear on levels specified by levspec.
• Position[expr, pattern, levspec, n] gives the positions of the first n objects found.

Notes

• Example: Position[

1+x^2, 5, x^4

, x^_]

• Position[expr, pattern] tests all the subparts of expr in turn to try and find ones that match pattern.

• Position returns a list of positions in a form suitable for use in Extract, ReplacePart and MapAt. The form is different from the one used in Part.

• The default level specification for Position is {0, Infinity}, with Heads -> True.

• A part specification {} returned by Position represents the whole of expr.

• Position[list, pattern, {1}, Heads -> False] finds positions only of objects that appear as complete elements of list.

• Level specifications are described in Section A.3.6.

• See Section 1.8.5, Section 2.1.7, Section 2.2.4 and Section 2.3.2.

• See also: Cases, Count, StringPosition, Ordering, SparseArray, ReplaceList, Insert, Delete.

• New in Version 1.

Further Examples