if-amb ( true false -- ? )
Simple backtracking non-determinism

Next:

amb-all ( quot -- )

Vocabulary
backtrack

Inputs

true	a quotation with stack effect ( -- ? )
false	a quotation

Outputs

?

a boolean

Word description
Execute the first quotation and return t if it returns t itself. If it fails with fail or returns f, then the second quotation is executed and f is returned.

Definition

USING: backtrack.private kernel ;

IN: backtrack

: if-amb ( true false -- ? )
    [
        [ { t f } amb ] [ [ must-be-true t ] compose ]
        [ [ f ] compose ] tri* if
    ] amb-preserve ; inline