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f/:lhs=.

removes any rules defined for lhs, associated with the symbol f.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Properties & Relations  
Possible Issues  
See Also
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TagUnset

f/:lhs=.

removes any rules defined for lhs, associated with the symbol f.

Details

  • Rules are removed only when their left‐hand side is identical to lhs, and the tests in Condition given on the right‐hand side are also identical.

Examples

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Basic Examples  (1)

Wolfram Language code: h/:f[h[x_]] := fh[x]
Wolfram Language code: h/:f[h[x_]]=.

Scope  (2)

Clear immediate definitions:

Wolfram Language code: sq/:area[sq] = s ^ 2;
Wolfram Language code: sq/:area[sq]=.

Clear delayed definitions:

Wolfram Language code: int/:rand[int] := RandomInteger[]
Wolfram Language code: int/:rand[int]=.

Properties & Relations  (1)

Use =. to clear definitions with a particular left-hand side:

Wolfram Language code: sq/:area[sq] = s ^ 2; sq/:circ[sq] = 4s;
Wolfram Language code: sq/:circ[sq]=.
Wolfram Language code: {area[sq], circ[sq]}

Clear all definitions:

Wolfram Language code: Clear[sq]
Wolfram Language code: Definition[sq]

Possible Issues  (1)

To clear an upvalue, the tag is required:

Wolfram Language code: h/:f[h[x_]] := fh[x]
Wolfram Language code: f[h[x_]]=.
Wolfram Language code: h/:f[h[x_]]=.
Wolfram Language code: Definition[h]
Wolfram Research (1988), TagUnset, Wolfram Language function, https://reference.wolfram.com/language/ref/TagUnset.html.

Text

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

CMS

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

APA

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

BibTeX

@misc{reference.wolfram_2026_tagunset, author="Wolfram Research", title="{TagUnset}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/TagUnset.html}", note=[Accessed: 13-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_tagunset, organization={Wolfram Research}, title={TagUnset}, year={1988}, url={https://reference.wolfram.com/language/ref/TagUnset.html}, note=[Accessed: 13-June-2026]}