Control

+P , +Q

Prove P and if it succeeds, then prove Q.

+P ; +Q

Prove P or Q.

\+ +Guard

If the guard Guard has a solution, fail, otherwise succeed.

+Guard -> +Q ; +R

+Q is called for every possible solutions of Guard. +R is only called if Guard has no solutions.

+Guard -> +Q

Analogous to +Guard -> +Q;fail

true

Always succeed.

fail

Always fail.

wait(+Goal)

Wait the full completion of the evaluation of Goal before evaluating its continuation. Still very experimental!

The library call provide the additionnal predicate:

call(Goal)

If Goal is instantiated to a term which would be acceptable as the body of a clause, then the goal call(Term) is executed exactly as if that term appeared textually in its place. There are some restrictions on Goal.