• ← Dispatch
• → ReplaceAll

Replace

WMA link

Replace[expr, x -> y]

yields the result of replacing expr with y if it matches the pattern x.

Replace[expr, x -> y, levelspec]

replaces only subexpressions at levels specified through levelspec.

Replace[expr, {x -> y, ...}]

performs replacement with multiple rules, yielding a single result expression.

Replace[expr, {{a -> b, ...}, {c -> d, ...}, ...}]

returns a list containing the result of performing each set of replacements.

• • Replace[x, {x -> 2}]

By default, only the top level is searched for matches:

• • Replace[1 + x, {x -> 2}]

• • Replace[x, {{x -> 1}, {x -> 2}}]

Replace stops after the first replacement:

• • Replace[x, {x -> {}, _List -> y}]

Replace replaces the deepest levels first:

• • Replace[x[1], {x[1] -> y, 1 -> 2}, All]

By default, heads are not replaced:

• • Replace[x[x[y]], x -> z, All]

Heads can be replaced using the Heads option:

• • Replace[x[x[y]], x -> z, All, Heads -> True]

Note that heads are handled at the level of elements:

• • Replace[x[x[y]], x -> z, {1}, Heads -> True]

You can use Replace as an operator:

• • Replace[{x_ -> x + 1}][10]