Crate lemma

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§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§

ArithmeticTerm: One operand of a NormalFormKind::Sum or NormalFormKind::Product. inverse marks a subtracted (Sum) or divided (Product) operand. The first term of a Sum/Product is never inverse.
BoundValueKind: Canonical suggestion/fill value plus the written measure unit when one was declared.
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.
EvaluateData: User-provided data values resolved against a plan’s type declarations.
ExecutableRule: A named rule’s root in the normal-form table, plus declaration metadata.
ExecutionPlan: A complete execution plan ready for the evaluator
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
KeyField: One field in a list’s row key: display name and resolved template data path.
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
NormalForm: One node in THE DAG: algebraic Kind, stamped result type, optional conversion span, optional fold origin, optional rule use-site identity.
NormalFormId: Index into a [NormalFormInterner] / shipped crate::planning::execution_plan::ExecutionPlan::normal_forms.
ParseResult
PathSegment: A single segment in a resolved path traversal
RatioUnit
RatioUnits
RationalInteger
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
ResolvedSpecTypes: Fully resolved types for a single spec. After resolution, all imports are inlined — specs are independent.
ResourceLimits: Limits to prevent abuse and enable predictable resource usage
Response: Response from evaluating a Lemma spec
RowInstance: A row instance: its spec, where it came from, and its bound fields.
RowRead: A member chain read on a row, through the row spec’s template plans: every end but the last reads a uses slot, as that instance; the last is the member read.
RulePath: Resolved path to a rule (created during planning from a rule reference).
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 own rules (empty path), and resolved temporal window. Source: [Engine::source]. Branch Rule leaves may name reachable imports that are not keys of Self::rules; follow those via show on the imported spec.
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.
SignatureFactor: One resolved unit in a signature: declared name, owning family, exponent.
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: one temporal slice of one version.
SpecInstance: The hops that name a spec instance, relative to the plan holding it: uses hops (rack.low), or a list hop with its row number (staff.2).
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
TypeFamily: Root of a custom type’s extension chain: the spec version that declares the root type, and its name. Types share a unit family only when they share this root declaration; a local money and an imported pricing.money are different families. Two versions of pricing declare different pricing <date>.money families; values from different versions do not mix. Interface drift across unpinned versions compares structure with LemmaType::same_interface, which ignores the family’s effective date.
TypedLiteral: Planning-time literal: value plus resolved type.
UnitIndex: Expression-scope units after bind: every declarer per bare unit name.
VetoExpression: A veto expression that prohibits any valid verdict from the rule

Enums§

ArithmeticComputation: Arithmetic computations
BranchOutcome: Outcome of inspecting a branch condition or a boolean operand.
CalendarPeriodUnit: Granularity of a calendar-period check.
CommandArg: A parsed constraint command argument, preserving the literal kind from the grammar rule command_arg: { number_literal | boolean_literal | text_literal | label }.
ComparisonComputation: Comparison computations
ConversionTraceRole
ConversionTypeKind: Primitive kind that can appear as an as conversion target. Excludes Text (display formatting is not a conversion) and the range kinds (a range is not a cast target — use a range literal or ... operator instead). The parser rejects as text at the as target position; data x: text declarations still use [PrimitiveKind::Text] via [crate::parsing::lexer::token_kind_to_primitive].
DataDefinition: Resolved data value for the execution plan: aligned with [DataValue] but with source per variant.
DataOrigin: Who wrote a data slot’s definition.
DataValue: Parse-time data value (before type resolution)
DateCalendarKind: Calendar-period membership checks.
DateGranularity
DateRelativeKind: Whether a date is relative to now in the past or future direction.
DispatchKey: One breakpoint in an ordered dispatch table.
DispatchRegion: One region body of a NormalFormKind::OrderedDispatch table.
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.
ExplainedListOp: List command identity on a narrated ExplanationNode::ListCommand.
ExplanationNode
InstallStep
LeafKind: Leaves in the shipped equation DAG: literals and data only.
ListKey: How a list addresses its rows.
ListPredKind
ListPredicateForm
LogicalConnective
MathematicalComputation: Mathematical computations
NormalFormKind: Algebraic structure only. Children are NormalFormId. Hash/Eq drive cons — no source spans or rule-ref identity here (those live on NormalForm).
NormalFormListOp
NumberArithmeticFailure
NumericFailure
OperationResult: Result of evaluating a rule, expression, or data leaf.
ParentType: Parent type in a type definition: built-in primitive or custom type name.
PiecewiseDecision: Where the Piecewise arm scan stopped. Arm 0 is the default; unless arms 1..arm_count are scanned from the highest index down, like the evaluator.
RangeBound: Which endpoint of a range lower / upper reads.
ReferenceTarget: What a DataDefinition::Reference copies its value from: either another data path or a rule whose result becomes this data’s value.
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
RoundingMode: Direction of a -> round|floor|ceil <step> command.
RowBinding: A field of a RowInstance.
RowEnd: Field of a row read through the row spec’s template plan.
RowOrigin: Where a row instance came from. Names missing fields and explanations.
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
UnitScale: Conversion factor of a measure unit: a plan-time rational, or a data/rule reference whose value is known only during evaluation.
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§

arithmetic_operation: Perform type-aware arithmetic operation, returning OperationResult (Veto for runtime errors).
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).
checked_div
checked_mul
comparison_operation: Perform type-aware comparison, returning OperationResult (Veto on error).
condition_outcome: How a piecewise unless-arm condition or a logical operand decides.
convert_unit_operand: Apply a type cast when the operand is already held as BoundValueKind.
decimal_to_rational
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.
negated_comparison: Logical computation operators (defined in semantics, not used by the parser). Returns the logical negation of a comparison (used by De Morgan / NOT-normal-form rewriting).
number_arithmetic
numbered_row_origin: 1-based numbered origin of a list row (items.2).
parse
parse_data_value
parse_spec_set_id: Validate and normalize a spec set identifier (a spec name in the default repository).
piecewise_decision: Scan unless-arm conditions high to low. outcome(arm) reports the condition’s decision, or None when there is none to read.
primitive_number_arc
rational_new
region_count: Number of regions for boundary_count breakpoints.
region_of_scrutinee: Region index for an evaluated, non-veto scrutinee value. The one decision procedure shared by value evaluation, explain’s winner check and missing_data liveness. A calendar or rational failure is the veto the dispatch evaluates to. A value kind the fold excludes is a planning bug.
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
SignatureIndex: Reverse index mapping a resolved unit signature to the unit (by name) and its owning measure type.

Crate lemma

Crate lemma Copy item path

§Lemma Engine

Re-exports§

Modules§

Structs§

Enums§

Constants§

Traits§

Functions§

Type Aliases§

Crate lemma