Patterns | Wolfram Language Fast Introduction for Programmers

Patterns

Notes for Java programmers:

The Wolfram Language's pattern language lets you describe patterns for arbitrary symbolic structures, allowing powerful regex-like manipulation to be generalized to any expression and any form of data.

Notes for Python programmers:

Patterns stand for classes of expressions. The basic pattern construct _ (pronounced "blank") stands for any expression.

Find cases in a list matching the pattern f[_]:

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x_ (short for x:_) stands for a pattern whose value will be named x:

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/. means "replace everywhere":

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Notes for Java programmers:

The sort of structural metaprogramming shown here is unique to the Wolfram Language's symbolic structure.

Notes for Python programmers:

The structural metaprogramming shown here, which treats code and data in the same way, is unique to the Wolfram Language's symbolic structure.

__ ("double blank") stands for any sequence of expressions:

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a | b | c stands for a, b or c:

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Notes for Java programmers:

This usage of | resembles Java's regex notation, although in Java | can also indicate a bitwise OR.

Notes for Python programmers:

| is used in Wolfram Language patterns similarly to its use in Python's regular expressions. However, in the Wolfram Language, | works for any type of symbolic pattern matching, not just for strings.

It works in heads too:

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