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.. rst-class:: align-right

built-in method

.. index:: pair: forall/2; Built-in method .. _methods_forall_2:

forall/2

Description

::

forall(Generator, Test)

For all solutions of Generator, Test is true. This meta-predicate implements a generate-and-test loop using a definition equivalent to \+ (Generator, \+ Test). As a consequence, no variables in the arguments are bound by a call to this predicate. This predicate often provides a better alternative to a failure-driven loop as an unexpected Test failure will not be ignored as it will make the forall/2 call fail.

This built-in meta-predicate is declared as a private method and thus cannot be used as a message to an object.

Meta-predicate template

::

forall(0, 0)

Modes and number of proofs

::

forall(@callable, @callable) - zero_or_one

Errors

| Either Generator or Test is a variable: | instantiation_error | Generator is neither a variable nor a callable term: | type_error(callable, Generator) | Test is neither a variable nor a callable term: | type_error(callable, Test)

Examples

| To call both goals in the context of the object or category containing the call: | forall(Generator, Test) | To send both goals as messages to :term:self: | forall(::Generator, ::Test) | To send both goals as messages to explicit objects: | forall(Object1::Generator, Object2::Test)

.. seealso::

:ref:methods_bagof_3, :ref:methods_findall_3, :ref:methods_findall_4, :ref:methods_setof_3