Common built-in predicates for Prolog, a summary
(don't be surprised if your interpreter has more/less built-in 
predicates; besides, you don't have to remember them all):


Build up of goals	:- , ; call not (or \+)

Build up of 
arithmatic expressions	is + - * / mod

Boolean expressions	= == true fail

Numbers			= < > >= =< =:=

Input/output		read write nl
			get0 get skip put tab display

File handling		see seeing seen tell telling told
			consult reconsult

Type checking   	var nonvar atom integer atomic

Meta-clauses		listing clause assert retract
			asserta assertz
			functor arg =.. name

Miscellaneous		statistics repeat op ! 
			setof bagof (findall)

Debugging		trace notrace spy nospy debugging nodebug