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Unset

lhs=.

removes any rules defined for lhs.

Details

Rules are removed only when their left‐hand sides are identical to lhs, up to renaming of patterns.
Unset[Once[expr]] removes any stored value for Once[expr].

Examples

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Basic Examples (2)

Undefine a value:

Undefine a function:

Scope (2)

Clear values of variables:

Clear functions (downvalues):

Properties & Relations (2)

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

Clear all definitions:

Use Unset[Once[expr]] to clear a remembered value of Once:

Possible Issues (1)

To clear an upvalue, the tag has to be given:

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