Enum PrologError 

pub enum PrologError {
    Instantiation {
        context: String,
    },
    Type {
        expected_type: &'static str,
        culprit: Term,
        context: String,
    },
    Existence {
        object_type: &'static str,
        culprit: Term,
        context: String,
    },
    Domain {
        expected_domain: &'static str,
        culprit: Term,
        context: String,
    },
    Evaluation {
        kind: &'static str,
        context: String,
    },
    Permission {
        operation: &'static str,
        permission_type: &'static str,
        culprit: Term,
        context: String,
    },
    Representation {
        flag: &'static str,
        context: String,
    },
    Resource {
        kind: &'static str,
        context: String,
    },
    Syntax {
        context: String,
    },
}

ISO formal-error vocabulary.

Variants

Instantiation

An argument that must be bound was unbound.

Fields

context: String

Type

An argument has the wrong type. expected_type is an atom name (e.g. “integer”, “atom”, “callable”); culprit is the offending term.

Fields

expected_type: &'static str

culprit: Term

context: String

Existence

An object referred to by the goal does not exist. object_type is e.g. “procedure”; culprit is the indicator.

Fields

object_type: &'static str

culprit: Term

context: String

Domain

An argument is outside the valid domain.

Fields

expected_domain: &'static str

culprit: Term

context: String

Evaluation

Arithmetic evaluation failed (zero divisor, overflow, etc.).

Fields

kind: &'static str

context: String

Permission

Operation not permitted.

Fields

operation: &'static str

permission_type: &'static str

culprit: Term

context: String

Representation

Implementation-defined representation limit exceeded.

Fields

flag: &'static str

context: String

Resource

Resource limit exhausted. Note: Resource { kind: "steps", ... } is the step-limit error and is intentionally uncatchable — see is_uncatchable.

Fields

kind: &'static str

context: String

Syntax

Syntax error during runtime term construction (e.g. number_chars/2).

Fields

context: String

Implementations

impl PrologError

pub fn is_uncatchable(&self) -> bool

Step-limit and other safety-ceiling errors must not be catchable by catch/3 — otherwise a malicious rule could loop indefinitely by trapping its own timeout. The solver checks this before consulting the catch stack.

pub fn to_term(&self, interner: &mut StringInterner) -> Term

Render as the ISO term error(Formal, Context). Formal matches the variant (e.g. type_error(integer, foo)); Context is the human-readable atom (the message string interned as an atom). Test helpers grep this string for substrings.

pub fn context(&self) -> &str

The human-readable context message. This is what test helpers substring-match against and what the CLI shows.

pub fn to_display(&self, interner: &mut StringInterner) -> String

Render the error term as a human-readable string. Used by the CLI and the test helper for substring assertions.

Trait Implementations

impl Clone for PrologError

fn clone(&self) -> PrologError

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PrologError

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

Formats the value using the given formatter.