`Position`¶

Finds all positions of a pattern in a list.

$ wo 'Position[{a, b, a, c, a}, a]'
{{1}, {3}, {5}}

$ wo 'Position[{1, 2, 3, 2, 1}, 2]'
{{2}, {4}}

$ wo 'Position[{1, 2, 3}, 4]'
{}

$ wo 'Position[{x, y, x, z}, x]'
{{1}, {3}}

The four-argument form Position[expr, pattern, levelspec, n] returns at most n positions, in scan order:

$ wo 'Position[{a, b, a, c, a, b, a}, a, Infinity, 2]'
{{1}, {3}}

$ wo 'Position[{1, {2, 3}, {4, {5, 6}}}, _Integer, Infinity, 4]'
{{1}, {2, 1}, {2, 2}, {3, 1}}

Position¶