Global variables (not in ISO)

A global variable has a name F/N and a value associated with it. A name cannot be used at the same time as both a global variable name and a predicate name.

• global_set(F,N,Value):   Set the value of the global variable F/N to Value. After this call, the name F/N becomes a global variable. If the name F/N was used as a predicate name, then all the information about the predicate will be erased.

• global_set(F,Value):   Equivalent to global_set(F,0,Value).

• global_get(F,N,Value):   The value associated with the global variable F/N is Value. If F/N is not a global variable, then the call fails.

• global_get(F,Value):   Equivalent to global_get(F,0,Value).

• is_global(F,N):   Test if F/N is a global variable.

• is_global(F): Equivalent to is_global(F,0).