Head—Wolfram Language Documentation (original) (raw)
BUILT-IN SYMBOL
Head
Head[expr]
gives the head of expr.
Head[expr,h]
wraps the result with h.
Examples
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Basic Examples (3)
The head of a function:
The head of a list:
The heads of atomic expressions:
Scope (3)
The head of a function entered with an operator:
The head of a compound expression:
Wrap the result in Hold to prevent the result from evaluating:
Without the second argument, the InverseFunction expression would evaluate:
Applications (2)
Find the cases with a head of Integer:
Verify the result:
Define a function that extracts the head and guarantees no evaluation occurs:
Without the HoldComplete, a Function object would be returned:
Properties & Relations (2)
The head is the part with index 0:
Head[e,f] is effectively equivalent to Extract[e,0,f]:
Possible Issues (1)
Neat Examples (1)
Head always eventually burrows to a symbol:
Related Links
- Fast Introduction for Programmers: Symbolic Expressions
- An Elementary Introduction to the Wolfram Language : Expressions and Their Structure
Wolfram Research (1988), Head, Wolfram Language function, https://reference.wolfram.com/language/ref/Head.html (updated 2020).
Text
Wolfram Research (1988), Head, Wolfram Language function, https://reference.wolfram.com/language/ref/Head.html (updated 2020).
CMS
Wolfram Language. 1988. "Head." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2020. https://reference.wolfram.com/language/ref/Head.html.
APA
Wolfram Language. (1988). Head. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Head.html
BibTeX
@misc{reference.wolfram_2025_head, author="Wolfram Research", title="{Head}", year="2020", howpublished="\url{https://reference.wolfram.com/language/ref/Head.html}", note=[Accessed: 17-June-2025 ]}
BibLaTeX
@online{reference.wolfram_2025_head, organization={Wolfram Research}, title={Head}, year={2020}, url={https://reference.wolfram.com/language/ref/Head.html}, note=[Accessed: 17-June-2025 ]}