Enum PathOp 

pub enum PathOp {
    Attr(RawId),
    NotAttr(RawId),
    Concat,
    Union,
    Star,
    Plus,
    Optional,
    Inverse,
}

Postfix-encoded path operations (used by the path! macro).

The macro compiles a path expression into a sequence of these operations. RegularPathConstraint::new converts the postfix sequence into a tree for evaluation.

Variants

Attr(RawId)

Single-attribute hop: traverse the given attribute.

NotAttr(RawId)

Negated single-attribute hop: traverse any attribute other than the given one (corresponds to SPARQL 1.1 §9.4’s negated property set !p). Used in (!p)+ / (!p)* to enumerate reachability under “anything but this predicate” edges.

Concat

Concatenation: compose the two preceding sub-expressions.

Union

Alternation: match either of the two preceding sub-expressions.

Star

Reflexive-transitive closure (*): zero or more repetitions.

Plus

Transitive closure (+): one or more repetitions.

Optional

Zero-or-one (?): match the preceding sub-expression once or not at all. Semantically Optional(p) ↔ Union(Identity, p), but recognised inline so the zero-step branch reuses the bound start node directly instead of materialising every node.

Inverse

Inverse (^): reverse the direction of the preceding sub- expression. ^p traverses p backwards (object → subject). Compound expressions (^(a/b), ^(a+)) are normalised at from_postfix time: Inverse is pushed down to Attr leaves via the standard rewrites ^(a/b) ↔ ^b/^a, ^(a|b) ↔ ^a|^b, ^(a+) ↔ (^a)+, etc.

Trait Implementations

impl Clone for PathOp

fn clone(&self) -> PathOp

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.