Crate lemma 

Lemma Engine

Rules for man and machine

Consumer API: load → specs → show / source → evaluate.

Re-exports

pub use api::evaluate_data_value_from_json_value;

pub use api::parse_evaluate_data_object;

pub use api::resolve_evaluate_rules;

pub use api::show_document;

pub use api::evaluate_data_value_from_json_value as run_data_value_from_json_value;

pub use api::parse_evaluate_data_object as parse_run_data_object;

pub use api::resolve_evaluate_rules as resolve_run_rules;

pub use result_value::CalendarResult;

pub use result_value::RangeResult;

pub use result_value::RowReference;

pub use result_value::RowResult;

pub use result_value::RuleResultValue;

pub use result_value::RuleResultValueFailure;

pub use result_value::SpecResult;

pub use result_value::SpecRuleResult;

pub use quality::Recommendation;

Modules

api

JSON API types for Engine boundary documents.

deps

Dependency layout under <workdir>/lemma_deps/, shared by CLI install and LSP.

documentation

Embedded language guides and example specs.

mcp

Pure Lemma MCP tools: Engine + arguments in, catalog or text out.

quality

Structural quality analysis over loaded specs.

result_value

API value for a rule result, ShowData.value, or ShowData.suggestion.

Structs

Cause

Context

Ordered store of specs keyed by (repository, name) and grouped into LemmaSpecSets.

DataPath

Resolved path to a data (created during planning from AST DataReference)

DateTimeValue

Engine

Engine for evaluating Lemma rules.

EngineError

Flat wire view of Error matching EngineError in engine/schemas/api.v1.json and engine/packages/npm/lemma.d.ts. Missing optionals serialize as JSON null.

EngineErrorSource

Source location attached to an EngineError. Line and column are 1-based; length is the UTF-8 byte length of the offending span.

ErrorDetails

Detailed error information with optional source location.

Errors

Load failure: errors plus the source texts we attempted to load.

ExplainedRule

One narrated rule body stored in an explanation’s rules table.

ExplainedRuleId

Compact id of a rule in an crate::evaluation::explanations::Explanation’s rules table. Assigned in first-reach order from the root.

Explanation

Fetch

Header

HttpResponse

IndexMap

A hash table where the iteration order of the key-value pairs is independent of the hash values of the keys.

Install

LemmaBase

LemmaBase registry: bound to https://lemmabase.com. Not configurable.

LemmaData

LemmaRepository

A Lemma repository header. Identity carrier; never owns specs.

LemmaSpec

A Lemma spec containing data and rules.

LemmaSpecSet

All spec versions sharing a (repository, name) identity, keyed by effective_from.

LemmaType

Resolved type after planning

Lexer

LiteralValue

Runtime literal payload. Type lives on NormalForm.result_type / DataDefinition / explicit computation parameters — not on the value.

MeasureUnit

A single unit within a Measure type.

MeasureUnits

ParseResult

PathSegment

A single segment in a resolved path traversal

RatioUnit

RatioUnits

Registries

The registries the host composes. Default is LemmaBase alone.

RegistryBundle

RegistryError

Repository

Repository group from Engine::specs.

RepositoryInstallResult

Result of Install: LemmaBase repository source text and normalized id.

RepositoryQualifier

Textual repository qualifier as written in source (for example @iso/countries). name stores the qualifier verbatim, including a leading @ when present. The planner resolves a RepositoryQualifier to an Arc<LemmaRepository> against the active context.

Resolve

ResourceLimits

Limits to prevent abuse and enable predictable resource usage

Response

Response from evaluating a Lemma spec

RuleResult

Result of evaluating a single rule. Struct fields match the API JSON shape.

SerializedConversionTraceStep

Show

Consumer [Engine::show] result: local offered types, inputs rules need, this spec’s rule graph (local rules plus reachable imports), and resolved temporal window. Source: [Engine::source].

ShowBranch

One arm of a rule’s flat last-match table on Show.

ShowData

One data entry in a Show.

ShowRule

Local rule on Show: result type, authored branches, stored topo deps.

Source

Positional source location: source id and span.

Span

Span representing a location in source code

SpecDependency

One uses target from a spec version’s source.

SpecIdentity

Resolved spec a value or rule result refers to.

SpecRef

A spec reference written in source.

SpecVersion

One temporal spec version from Engine::specs.

TimezoneValue

UTC offset in signed whole minutes; |offset_minutes| is at most 23:59.

TransportFailure

Enums

CommandArg

A parsed constraint command argument, preserving the literal kind from the grammar rule command_arg: { number_literal | boolean_literal | text_literal | label }.

ConversionTraceRole

DataValue

Parse-time data value (before type resolution)

DateGranularity

EffectiveDate

Error

Error types for the Lemma system with source location tracking

ErrorKind

Classification of an Error. Serialized as the kind field on the flat object returned to JavaScript from WASM (engine/src/wasm.rs, JsError).

EvaluateDataValue

Neutral overlay tree. [EvaluateData::resolve] reads each value by declared type.

ExplanationNode

InstallStep

ListKey

How a list addresses its rows.

OperationResult

Result of evaluating a rule, expression, or data leaf.

ParentType

Parent type in a type definition: built-in primitive or custom type name.

RegistryErrorKind

The kind of failure that occurred during a Registry operation.

RequestErrorKind

Distinguishes HTTP 404 (not found) from 400 (bad request) for request errors.

ResolveStep

ShowConversionTarget

Conversion target on a Show as expression (no owning type — inspection only).

ShowExpression

Resolved expression tree for Show branches (tag = "type" on the API mirror).

SourceType

TokenKind

TypeConstraintCommand

Constraint command for type definitions. Derived from lexer tokens; no string matching.

TypeSpecification

ValueKind

Value payload (shape of a literal).

VetoType

Why an operation yielded no value (domain veto).

Constants

API_V1_SCHEMA_JSON

Checked-in JSON Schema for Show, Response, and related wire types (engine/schemas/api.v1.json). Regenerated by cargo run -p xtask -- schema.

COMPLETION_KEYWORD_LABELS

Spellings shared by [keyword_from_identifier] and LSP completion.

EMBEDDED_STDLIB_REPOSITORY

Repository name reserved for the embedded standard library (repo lemma, spec units). User Engine::load must not target this name via SourceType::Dependency.

MAX_DATA_NAME_LENGTH

MAX_RULE_NAME_LENGTH

MAX_SPEC_NAME_LENGTH

UNITS_LEMMA

Traits

HttpTransport

Synchronous driver for Rust hosts. wasm drives the steps itself with async fetch.

Registry

A registry is a request builder and response interpreter. It never performs I/O.

Functions

attribute_evaluate_data_error

Attribute a walker error to its top-level data key unless already attributed.

attribute_run_data_error

Attribute a walker error to its top-level data key unless already attributed.

can_be_label

Returns true if the token kind can be used as a label or reference segment (identifier, or one of the keywords past / future / permille / is in label position).

evaluate_data_from_entries

Top-level run-data entries from a host walker. Keys differing only in case: request Error.

evaluate_data_map_from_entries

Nested object entries from a host walker. Keys differing only in case: request Error.

evaluate_data_null_list_item

Host list item that is null (JSON null, JS null / undefined, Java null, Elixir nil). A list has no unsupplied row, so this is a request Error, never an omitted item. position is 1-based within its list.

format_explanation

format_parse_result

Format a ParseResult (repository groups + specs) into canonical Lemma source.

format_repositories

Text view of Engine::specs, as lemma specs prints it.

format_source

Parse a source string and format it to canonical Lemma source.

format_specs

Format a sequence of parsed specs into canonical Lemma source.

numbered_row_origin

1-based numbered origin of a list row (items.2).

parse

parse_spec_set_id

Validate and normalize a spec set identifier (a spec name in the default repository).

resolve_effective

Resolve an optional effective datetime string for planning or evaluation.

row_field_input_key

Input key of a field of a numbered list row (items.2.weight).

run_data_from_entries

Top-level run-data entries from a host walker. Keys differing only in case: request Error.

run_data_map_from_entries

Nested object entries from a host walker. Keys differing only in case: request Error.

run_data_null_list_item

Host list item that is null (JSON null, JS null / undefined, Java null, Elixir nil). A list has no unsupplied row, so this is a request Error, never an omitted item. position is 1-based within its list.

try_parse_type_constraint_command

Parses a constraint command name. Returns None for unknown (parser returns error).

type_detail_lines

Produce a human-readable summary of type constraints, or None when there are no constraints worth showing (e.g. bare boolean). Returns one formatted string per constraint or property of the type specification. Uses display_str for all rational bounds so they render as decimals, not as raw fractions.

Type Aliases

RunDataValueDeprecated