PLOGHELP PROLOG_EVALTRUE                   Robert Duncan, September 1988


    ?- prolog_evaltrue(Expr).


Evaluates the term -Expr- as a POP-11 expression and succeeds if the
result is non-false. The rules for evaluation are the same as those
described in PLOGHELP * PROLOG_EVAL.

Example:

A predicate which tests whether one atom is a subword of another
(-issubstring- is documented in HELP * ISSUBSTRING):

    subword(A, B) :-
        atom(A),
        atom(B),
        prolog_evaltrue(issubstring(quote(A), quote(B))).

    ?- subword(cat, dislocate).
    yes

    ?- subword(zebra, prestidigitation).
    no


-- RELATED DOCUMENTATION ----------------------------------------------

PLOGHELP * PROLOG_EVAL
    Evaluating Prolog terms as POP-11 expressions

--- C.all/plog/help/prolog_evaltrue
--- Copyright University of Sussex 1988. All rights reserved. ----------