• ← Replace
• → ReplaceList

ReplaceAll (/.)

WMA link

ReplaceAll[expr, x -> y]

expr /. x -> y

yields the result of replacing all subexpressions of expr matching the pattern x with y.

expr /. {x -> y, ...}

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

expr /. {{a -> b, ...}, {c -> d, ...}, ...}

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

• • a+b+c /. c->d

• • g[a+b+c,a]/.g[x_+y_,x_]->{x,y}

If rules is a list of lists, a list of all possible respective replacements is returned:

• • {a, b} /. {{a->x, b->y}, {a->u, b->v}}

The list can be arbitrarily nested:

• • {a, b} /. {{{a->x, b->y}, {a->w, b->z}}, {a->u, b->v}}

• • {a, b} /. {{{a->x, b->y}, a->w, b->z}, {a->u, b->v}}

ReplaceAll also can be used as an operator:

• • ReplaceAll[{a -> 1}][{a, b}]

ReplaceAll replaces the shallowest levels first:

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