Particularly when you use transformation rules, you often need to name pieces of patterns. An object like x_ stands for any expression, but gives the expression the name x. ...

Patterns are used throughout Mathematica to represent classes of expressions. A simple example of a pattern is the expression f[x_]. This pattern represents the class of ...

Introduction Finding Expressions That Match a Pattern Naming Pieces of Patterns

The general symbolic string patterns in Mathematica allow you to perform powerful string manipulation efficiently. What follows discusses the details of string 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 ...

Mathematica's symbolic string patterns provide a compact yet readable basis for sophisticated string operations. Included directly in programs, or symbolically generated on ...

Verbatim patterns. Here the x_ in the rule matches any expression. The Verbatim tells Mathematica that only the exact expression x_ should be matched.

LinkPatterns[link] gives a list of the patterns for which definitions were set up when the external program associated with the specified MathLink connection was installed.

Repeated patterns. Multiple blanks such as x__ allow you to give patterns in which sequences of arbitrary expressions can occur. The Mathematica pattern repetition operators ...

Introduction General String Patterns Regular Expressions