Clear

Clear[symbol1,symbol2,]

clears values and definitions for the symboli.

Clear["form1","form2",]

clears values and definitions for all symbols whose names match any of the string patterns formi.

Details

  • Clear does not clear attributes, messages, or defaults associated with symbols.
  • Clear allows abbreviated string patterns containing the following metacharacters:
  • *zero or more characters
    @one or more characters, excluding uppercase letters
    \\*, etc.literal *, etc.
  • Clear["context`*"] clears all symbols in a particular context.
  • Clear is HoldAll.
  • Clear does not affect symbols with the attribute Protected.

Examples

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Basic Examples  (2)

Clear a variable:

Clear a function definition:

Scope  (4)

Clear values of variables:

Clear functions (downvalues):

Clear upvalues:

Clear several symbols:

Generalizations & Extensions  (2)

Clear all symbols in a given context:

Specify symbols to clear as string patterns:

Applications  (1)

Clear any old definitions before making new ones:

Properties & Relations  (2)

Clear does not remove defaults, options, or attributes:

Use ClearAll to clear everything:

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

Clear all definitions:

Possible Issues  (1)

Protected symbols cannot be cleared:

Use Unprotect to clear definitions of protected symbols:

Neat Examples  (1)

Clear the definitions of all symbols in the current context:

Introduced in 1988
 (1.0)