Cases [{e1,e2,…},pattern]
gives a list of the ei that match the pattern.
Cases [{e1,…},patternrhs]
gives a list of the values of rhs corresponding to the ei that match the pattern.
Cases [expr,pattern,levelspec]
gives a list of all parts of expr on levels specified by levelspec that match the pattern.
Cases [expr,patternrhs,levelspec]
gives the values of rhs that match the pattern.
Cases [expr,pattern,levelspec,n]
gives the first n parts in expr that match the pattern.
Cases
Cases [{e1,e2,…},pattern]
gives a list of the ei that match the pattern.
Cases [{e1,…},patternrhs]
gives a list of the values of rhs corresponding to the ei that match the pattern.
Cases [expr,pattern,levelspec]
gives a list of all parts of expr on levels specified by levelspec that match the pattern.
Cases [expr,patternrhs,levelspec]
gives the values of rhs that match the pattern.
Cases [expr,pattern,levelspec,n]
gives the first n parts in expr that match the pattern.
Details and Options
- The first argument to Cases need not have head List .
- When used on an Association , Cases picks out elements according to their values.
- Cases [expr,pattern:>rhs] evaluates rhs only when the pattern is found.
- Cases [pattern][list] is equivalent to Cases [list,pattern].
- Cases uses standard level specifications:
-
n levels 1 through n{n} level n only{n1,n2} levels n1 through n2
- The default value for levelspec in Cases is {1}.
- A positive level n consists of all parts of expr specified by n indices.
- A negative level -n consists of all parts of expr with depth n.
- Level -1 consists of numbers, symbols, and other objects that do not have subparts.
- Level 0 corresponds to the whole expression.
- With the option setting Heads->True , Cases looks at heads of expressions, and their parts.
- Cases traverses the parts of expr in a depth-first order, with leaves visited before roots.
- Parallelize [Cases[expr,pattern]] or ParallelCases [expr,pattern] computes Cases [expr,pattern] in parallel on all subkernels. »
Examples
open all close allBasic Examples (4)
Find cases that explicitly match integers:
Find cases that do not match integers:
Return the x from inside each f[x_] matched:
Use the operator form of Cases :
Pick elements from an Association :
Scope (10)
Find all cases of lists of two elements:
Find the sum of every pair of elements:
Pick out elements that are not 0:
Pick out cases of integers down to level 2:
Return only the first three matching elements:
Use :> to evaluate only after explicit elements have been found:
Find all possible subexpressions at any level:
Find all possible subexpressions at any level, including the head of the expression:
Pick elements from nested associations:
Pick elements from a List matching an Association :
Find keys of each matching Association :
Pick pairs of keys from each association in a list:
Find associations with the key satisfying a condition:
Options (1)
Heads (1)
Find symbols among the elements of an expression:
Also include the head of the expression in the search:
Properties & Relations (2)
Possible Issues (1)
A rule transforms the matching elements into its right side:
Use HoldPattern to treat the rule itself as a pattern:
See Also
FirstCase Select BinLists GatherBy Position MemberQ Count SequenceCases StringCases ReplaceList Collect DeleteCases Except ParallelCases
Function Repository: UniqueCases PositionedCases MapCases HighlightCases GroupCases
Tech Notes
Related Workflows
- Import Tabular Data from a Notebook
History
Introduced in 1988 (1.0) | Updated in 2003 (5.0) ▪ 2014 (10.0)
Text
Wolfram Research (1988), Cases, Wolfram Language function, https://reference.wolfram.com/language/ref/Cases.html (updated 2014).
CMS
Wolfram Language. 1988. "Cases." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/Cases.html.
APA
Wolfram Language. (1988). Cases. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Cases.html
BibTeX
@misc{reference.wolfram_2025_cases, author="Wolfram Research", title="{Cases}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/Cases.html}", note=[Accessed: 17-November-2025]}
BibLaTeX
@online{reference.wolfram_2025_cases, organization={Wolfram Research}, title={Cases}, year={2014}, url={https://reference.wolfram.com/language/ref/Cases.html}, note=[Accessed: 17-November-2025]}