Pattern

sym:obj or Pattern[sym,obj]

represents the pattern object obj, assigned the name sym.

Details

  • The name sym must be a symbol.
  • The object obj can be any pattern object.
  • When a transformation rule is used, any occurrence of s on the right‐hand side is replaced by whatever expression it matched on the left‐hand side.
  • The operator : has a comparatively low precedence. The expression x:_+_ is thus interpreted as x:(_+_), not (x:_)+_.
  • The form s_ is equivalent to s:_. Similarly, s_h is equivalent to s:_h, s__ to s:__, and so on. »

Examples

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Basic Examples  (1)

Give a name to lists of integers:

Scope  (1)

Use Pattern in any pattern-matching function including ReplaceAll:

Cases:

And MatchQ:

Properties & Relations  (1)

The forms s_ and s:_ are equivalent:

This extends to forms with a specified head:

As well as forms involving BlankSequence and BlankNullSequence:

Possible Issues  (1)

The input s:v is a form of Pattern only if s is a symbol:

If s is a special input form for Blank[…] or Pattern[sym,Blank[…]], then s:v is Optional[s,v]:

Forms involving BlankSequence[…] and BlankNullSequence[…] are similar:

If s is any other expression, the form is not valid input:

Wolfram Research (1988), Pattern, Wolfram Language function, https://reference.wolfram.com/language/ref/Pattern.html.

Text

Wolfram Research (1988), Pattern, Wolfram Language function, https://reference.wolfram.com/language/ref/Pattern.html.

CMS

Wolfram Language. 1988. "Pattern." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Pattern.html.

APA

Wolfram Language. (1988). Pattern. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Pattern.html

BibTeX

@misc{reference.wolfram_2024_pattern, author="Wolfram Research", title="{Pattern}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/Pattern.html}", note=[Accessed: 21-December-2024 ]}

BibLaTeX

@online{reference.wolfram_2024_pattern, organization={Wolfram Research}, title={Pattern}, year={1988}, url={https://reference.wolfram.com/language/ref/Pattern.html}, note=[Accessed: 21-December-2024 ]}