Rules & Patterns

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

ReferenceReference

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