Struct Builder 

pub struct Builder { /* private fields */ }

Deterministic state machine for graph construction.

The builder enforces all structural constraints:

• No duplicate ID definitions
• No forward references (DAG property)
• Resource limits (max nodes, depth, inputs, outputs)

Implementations

impl Builder

pub fn new() -> Self

Create a new builder with default limits.

pub fn with_limits(limits: Limits) -> Self

Create a new builder with custom limits.

pub fn phase(&self) -> Phase

Get the current build phase.

pub fn is_completable(&self) -> bool

Check if the graph is in a completable state.

Returns true when:

• At least one output has been declared
• No node definition is in progress
• We’re ready for another output (not mid-declaration)

This is useful for LLM decoding where we want to know if generation can stop, even though more outputs could be added.

pub fn push(&mut self, token: Token) -> Result<(), BuildError>

Feed a single token to the builder.

pub fn finish(self) -> Result<Graph, BuildError>

Finalize and return the graph.

Errors

Returns an error if:

• A node definition is incomplete
• No outputs have been declared

pub fn valid_next_tokens(&self) -> Vec<Token>

Returns the set of valid next tokens for LLM logit masking.

This is the critical interface for constraining LLM output. By masking all logits except those corresponding to valid tokens, the LLM is guaranteed to produce a syntactically correct circuit.

Trait Implementations

impl Debug for Builder

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Builder

fn default() -> Self

Returns the “default value” for a type.