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In RELFUN, declarations are realized via declare facts (in contrast to PROLOG, where declarations are usually goals, i.e. they are preceded by ``:-'').

LL functions, which should be accessed from REL, have to be declared:

Mode declarations have the following form:
declare( mode[[]] ). where the are either g or x (corresponding to and in section 4.2.2).

For example, the mode declarations for append and reverse are

If a predicate should additionally be declared to be representable as a (total) deterministic function (as was mentioned in subsection, mode is replaced by dfmode: declare(dfmode[append[g,g,x]]).

In appendix C, the usage of mode declarations is illustrated.

Harold Boley & Michael Sintek (