Patterns
Video Version
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:
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.
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[_]:
x_ (short forx:_) stands for a pattern whose value will be namedx:
/. means "replace everywhere":
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:
a |b |c stands fora,b orc:
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:
_h stands for any expression with headh:
QUICK REFERENCE:Operations Involving Patterns