is ( quot: ( env -- value ) dist -- goal )

Vocabulary

logic

Inputs

quot	a quotation
dist	a logic predicate

Outputs

goal	a logic-goal

Word description

Takes a quotation and a logic variable to be unified. Each of the two quotations takes an environment and returns a value. is returns the internal representation of the goal. is is intended to be used in a quotation. If there is a quotation in the definition of rule, logic uses the internal definition of the goal obtained by calling it.

Definition

USING: accessors combinators formatting kernel logic.private
sequences ;

IN: logic

:: is ( quot: ( env -- value ) dist -- goal )
    quot collect-logic-vars dup dist swap member?
    [ dist suffix ] unless
    :> args quot dist "[ %u %s is ]" sprintf <pred> :> is-pred
    is-pred args logic-goal boa :> is-goal V{
        {
            is-goal
            [| env |
                env dist env quot ( env -- value ) call-effect
                unify
            ]
        }
    } is-pred defs<< is-goal ;