mode/2 — The Logtalk Handbook v3.47.0 documentation

# `mode/2`

## Description

    mode(Mode, NumberOfProofs)

Most predicates can be used with several instantiations modes. This directive enables the specification of each instantiation mode and the corresponding number of proofs (not necessarily distinct solutions). You may also use this directive for documenting grammar rule non-terminals.

## Template and modes

    mode(+predicate_mode_term, +number_of_proofs)
    mode(+non_terminal_mode_term, +number_of_proofs)

## Examples

    :- mode(atom_concat(-atom, -atom, +atom), one_or_more).
    :- mode(atom_concat(+atom, +atom, -atom), one).

    :- mode(var(@term), zero_or_one).

    :- mode(solve(+callable, -list(atom)), zero_or_one).

See also

info/2, predicate_property/2