Built-In Predicates
   SICStus Prolog provides a wide range of built-in predicates to
perform all kinds of tasks; see the Table of Contents.
   
It is not possible to redefine built-in predicates.  An attempt to
do so will give an error message.  See Pred Summary.
   
When introducing a built-in predicate, we shall present its usage
with a mode spec, and optionally with an annotation containing one
or more of:
     
- ISO
     
 - The predicate complies with the ISO Prolog Standard. 
 - ISO only
     
 - The predicate variant described complies with the ISO Prolog Standard
and is valid in the 
iso execution mode only. 
 - SICStus only
     
 - The predicate variant described is valid in the 
sicstus execution
mode only. 
 - declaration
     
 - A declaration that can't be redefined as a predicate. 
 - development
     
 - The predicate is not available in runtime systems. 
 - extendible
     
 - The predicate is an extendible predicate. 
 - hook
     
 - The predicate is a hook predicate. 
 - hookable
     
 - The predicate is a hookable predicate. 
 - obsolescent
     
 - The predicate is obsolescent and should be avoided in new code. 
 - reserved
     
 - A reserved construct that can't be defined as a predicate. 
 
The following descriptions of the built-in predicates are grouped
according to the above categorization of their tasks.