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IsDefined

check if an expression has been defined

Syntax
IsDefined(E)

where E is a CoCoA expression.

Description
This function returns TRUE if E is defined, otherwise it returns false. Typically, it is used to check if a name has already been assigned. NOTE: this function used to be named Defined.

Example
IsDefined(MyVariable);
FALSE
-------------------------------
MyVariable := 3;
IsDefined(MyVariable);
TRUE
-------------------------------