pub struct ExClause<I: Interner> {
    pub subst: Substitution<I>,
    pub ambiguous: bool,
    pub constraints: Vec<InEnvironment<Constraint<I>>>,
    pub subgoals: Vec<Literal<I>>,
    pub delayed_subgoals: Vec<InEnvironment<Goal<I>>>,
    pub answer_time: TimeStamp,
    pub floundered_subgoals: Vec<FlounderedSubgoal<I>>,
}
Expand description

The paper describes these as A :- D | G.

Fields

subst: Substitution<I>

The substitution which, applied to the goal of our table, would yield A.

ambiguous: bool

True if any subgoals were depended upon negatively and were not fully evaluated, or if we encountered a CannotProve goal. (In the full SLG algorithm, we would use delayed literals here, but we don’t bother, as we don’t need that support.)

constraints: Vec<InEnvironment<Constraint<I>>>

Region constraints we have accumulated.

subgoals: Vec<Literal<I>>

Subgoals: literals that must be proven

delayed_subgoals: Vec<InEnvironment<Goal<I>>>

We assume that negative literals cannot have coinductive cycles.

answer_time: TimeStamp

Time stamp that is incremented each time we find an answer to some subgoal. This is used to figure out whether any of the floundered subgoals may no longer be floundered: we record the current time when we add something to the list of floundered subgoals, and then we can compare whether its value has changed since then. This is not the same TimeStamp of Forest’s clock.

floundered_subgoals: Vec<FlounderedSubgoal<I>>

List of subgoals that have floundered. See FlounderedSubgoal for more information.

Trait Implementations

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