lambda

lang/lambda

Thin facade for the lambda-calculus editor language. Re-exports the handful of types and functions that consumers (editor/ tests and ffi/lambda/) actually call through this path, sourced from the three currently-imported subpackages edits, eval, and companion. The other lambda subpackages (proj, flat) are not re-exported here — consumers that need them import the subpackage directly.

The facade was originally much larger; in 2026-05 it was trimmed to the symbols with live callers. Consumers that need more reach into the subpackages directly (see examples/ideal/main/moon.pkg).

Public API

Re-exported from lang/lambda/edits:

• type TreeEditOp
• type DropPosition (canonical origin is @core; lang/lambda/edits re-re-exports it, so consumers see it through either path)

Re-exported from lang/lambda/companion:

• type LambdaCompanion
• new_lambda_editor(agent_id, capture_timeout_ms?, parent_runtime?) -> (SyncEditor[Term], LambdaCompanion)
• apply_lambda_tree_edit(editor, companion, op, cursor)
• get_lambda_ast, get_lambda_ast_pretty, get_lambda_resolution, get_lambda_dot_resolved
• parse_tree_edit_op

Re-exported from lang/lambda/eval:

• type EvalResult

Consumers

• ffi/lambda/ — JS FFI surface; calls new_lambda_editor, apply_lambda_tree_edit, parse_tree_edit_op, and the AST/pretty accessors.
• editor/ (blackbox tests only) — uses @lambda.get_lambda_ast and related accessors to drive integration tests.
• examples/ideal/main/ — additionally uses LambdaCompanion, EvalResult, DropPosition, TreeEditOp; imports lang/lambda/edits directly for the rest.

Dependencies

lang/lambda/edits, lang/lambda/eval, lang/lambda/companion. The proj and flat subpackages exist but are not re-exported here; consumers that need them (none today) should import them directly.

Stability

Experimental — the lambda language is the reference implementation for new editor features. The facade surface evolves as features are wired up; expect re-exports to be added as new consumers appear.

Notes

There is no top-level logic in this package. Earlier revisions included a reconcile_ast.mbt file re-exporting @core.reconcile, which had no callers and was removed. The reference for incremental projection over the lambda AST lives in lang/lambda/flat (VersionedFlatProj, build_lambda_projection_memos); import that subpackage directly if needed.