This is documentation for Mathematica 9, which was
based on an earlier version of the Wolfram Language.
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Rules & Patterns

At the core of Mathematica's symbolic programming paradigm is the concept of transformation rules for arbitrary symbolic patterns. Mathematica's pattern language conveniently describes a very general set of classes of expressions, making possible uniquely readable, elegant and efficient programs.


Rules »

lhsrhs (Rule) representation of replacement rule

expr/.rules (ReplaceAll) apply replacement rules to an expression

RuleDelayed(:>) ▪ ReplaceRepeated(//.) ▪ Condition(/;) ▪ ...

Patterns »

x_ any expression, named

x__ sequence of expressions

a|b|c alternative forms

Repeated(..) ▪ Except ▪ Longest ▪ Shortest ▪ ...

Pattern Matching Functions »

Cases elements of a list or expression matching a given pattern

Position ▪ MemberQ ▪ MatchQ ▪ Count ▪ DeleteCases ▪ ...

Assignments »

lhs=rhs, lhs:=rhs make assignments for arbitrary patterns