CHANGELOG.md

Changelog for lambda-notebook

Unreleased

New features:

• Parsing-related features:
  • The syntax {:} can now be used for the empty map.
  • Non-python operators (e.g. =>) are now first-class operators, and can be defined independently of python operator symbols.
  • Precedence and associativity for binary operators are now configurable.
• Reference to types in the metalanguage, via the Type operator and a new reserved word type for writing type terms.
• Improvements to type defaults for terms, both the api and the defaults. The main obvious change is that terms beginning with p, q, and r default to type t as is typical in propositional logic.

Fixes, improvements, changes:

• Changes to parser behavior:
  • The parser has been completely rewritten and is now based on standard parsing techniques. This should be mostly opaque to the user, except for a few things noted in this changelog.
  • Binding expressions no longer have an absolute requirement for parens.
  • Various changes to operator precedence that diverge from python. Equality has a more standard precedence than before (when it was derived from %). >> and => have lower precedence than & and |. Unary operators now have highest precedence.
  • Many weirdnesses that resulted from running python's eval on semi-parsed code are eliminated.
  • Improvements and changes to parsing error messages.
• The deprecated CustomTerm has been removed.

[0.8.1] - Bugfix release - 2025-12-09

Fixes:

• Address some issues in colab rendering
• Widen supported IPython version to handle colab's old version

[0.8.0] - Metasemantics - 2025-11-12

This version involves a major metalanguage/type system update, centered around a new approach to metasemantics. This is probably the biggest set of changes since the initial release.

New features:

• Meta-meta-language features (new module, lamb.meta.meta):
  • MetaTerm: this is a major change/improvement to how constant values (e.g. True) work. A MetaTerm is a direct, immutable reference to a backing python object that provides a metasemantics for the term. This change goes together with an explicit implementation of domain sets of python objects, providing backing domains for all simple types (e.g. type e is backed by strings of a certain kind, SetType is backed by python sets, functions are backed by mappings/callables, etc).
  • Simplification guarantees complete simplification when dealing with MetaTerms. This change also allows simplification for quantified expressions with finite domains (by iterating over the type domain).
  • Evaluations: much richer support for truth-table-like batch evaluations of boolean expressions. truthtable is a handy wrapper function on this.
  • extract_boolean: given an arbitrary metalanguage expression, produce a purely boolean expression together with an assignment filling in the non-boolean parts.
  • An implementation of first-order model theory using the evaluation system.
• Metalanguage features
  • Set operations: intersection, union, difference. Core relations: equivalence, the various sub/superset relations.
  • Set-related simplification heuristics.
  • A ternary conditional operator Case
  • Operators Dom, Codom and Fun, as well as a sequencing operator + for working with functions.
  • A facade class for working with TypedExprs.
  • Improvements to operator handling, including the ability to define operators based on metalanguage functions.
  • Support for restricted quantification for existential and universal operators (and Iota).
• Type system features:
  • As noted above, the ontology for simple types is new essentially complete, at least for the finite case, by implementing domain sets.
  • Type domains allow domain restriction in order to work with finite examples. The easiest api for this is the context manager function restrict_domain on atomic types.
  • A new type constructor (∀) that unselectively binds type variables in its scope. This is only semi-intended to be user facing, as it isn't easy to understand. However, this directly supports the next feature:
  • Support for full let-polymorphism via assignments. That is, polymorphic functions in assignments can now have distinct specializations in the same expression (previously they would have to unify to a coherent type; let-polymorphism could only be achieved anonymously via reduction).
• Metalanguage "compilation": expressions with no free variables can now be converted to python code that runs roughly within an order of magnitude of similar code implemented directly in python. In many cases, this is much faster than simplification, and sometimes in a way that matters (especially with quantification in play). There are certain other caveats: finite sets only, equivalence of functions can't be dynamically determined.
• Simplification and expression manipulation features:
  • new module, lamb.meta.ply, hosts various code (new and old) for generic manipulation and introspection on TypedExpr objects.
  • term order normalization for n-ary operations where this is appropriate (e.g. &, |). This normalizes order and structure (to left commutivity). This approach allows keeping strict binary operators, but when appropriate, manipulating them as n-ary sequences.
  • more configurable simplification, with a number of options that may not be used by default. (Roughly building on SymPy's approach.) For example, the eliminate_sets option will convert set operations/relations to booleans where possible, though this may make formulas more complicated.
• Error / exception handling and display, especially in magic contexts, is rewritten. New context manager lamb.errors() allows clean handling of lambda notebook-specific errors.
• Composition:
  • compose order is now preserved and used in rendering for bottom-up composition.
  • composition objects now support a function source_tree(), which extracts an underlying nltk-style Tree for display.

Documentation and sample notebooks:

• New documentation for sets, meta-meta-language expressions
• Rewritten: Hamblin semantics fragment

Fixes, improvements, changes:

• types and related issues:
  • many internal improvements/changes to type inference. One thing to note is that internal type variables will now appear as ? followed by a number, rather than as I variables.
  • improvements to anonymous let-polymorphism, which was previously very non-general
  • Many bug fixes to do with polymorphism
• improvements to simplification with recursive Tuple expressions
• improvements to inference for Partial expressions.
• improvements to derivations. The most public-facing change is that derivation reasons are now visually aligned with the origin step, not the result step. These objects now better support introspection, as well.
• many improvements to metalanguage simplification and reduction heuristics.
• improvements to latex rendering compatibility, including colab (katex) and mathjax 3.
• Older support code has been removed

[0.7.1] - Bugfix release - 2024-04-22

Fixes:

• Rename a notebook to avoid a Windows filename issue

[0.7.0] - Rendering and metalanguage updates - 2023-09-27

New features:

• support rendering in colab
• quicker loading without the kernel (import lamb.auto)
• refactor metalanguage code: better support for new operators

Fixes:

• fix several polymorphic type inference issues
• improved ipython/jupyter rendering

[0.6.9] - Compatibility fix - 2022-06-18

Fix a python 3.10 compatibility bug

[0.6.8] - Vacuity improvements - 2021-10-18

Fixes, improvements, changes (highlights):

• correctly pin the right traitlets version

[0.6.7] - Vacuity improvements - 2021-10-18

New features:

• composition rule for index percolation in tree composition
• composition rule for vacuous nodes (with content=None)

Fixes, improvements, changes (highlights):

• improve and generalize lang.Binder behavior
• enable svgling for internal tree drawing
• improvements to the relative clause notebook

[0.6.6] - Bugfix release / python packaging - 2021-10-11

This is the first version that was released on PyPI.

New features:

• added an explicit changelog in this version. (Older changes in this document are backfilled from commit messages.)
• experimental support for derivations shown using svgling trees
• full support for installation in site-packages, better kernel installation

Fixes, improvements, changes (highlights):

• improve derivation rendering
• improve cross-browser compatibility
• improve error messaging and handling of composition failures

[0.6.5] - Bugfix release - 2018-10-10

Documentation and notebooks:

• Intensional scope fragment (primarily based on Keshet's work)

Fixes, improvements, changes (highlights):

• Test improvements
• Partiality rework
• CI (via Travis)
• repr improvements

[0.6.4] - Partiality and simplification - 2017-11-03

(Note: in conventional commit terms this should have definitely been a major version bump.)

New features:

• Change Predicate Abstraction based on Coppock's version in Semantics Boot Camp (now Coppock and Champollion)
• Recursive simplification for boolean expressions, numbers
• Lexical ambiguity in Items
• Metalanguage operator ExistsExact
• Initial implementation of Heim & Kratzer-style presuppositions via partiality
• Disjunctive type constructor, for ad-hoc polymorphism over simple types; and corresponding Disjunction objects in the metalanguage
• testing infrastructure, random expression generation

Documentation:

• New introductory demo notebook
• New fragment: compositional DRT (from Dee Ann Reisinger)
• Metalanguage quick reference

Fixes, improvements, changes (highlights):

• Fixes and improvements to polymorphism, better testing
• Improvements to composition systems, especially tree-based composition
• Improvements to rich reprs

[0.6.3] - Bugfix update - 2016-09-28

New feature:

• Allow spaces and underscores in Item names

Fixes, improvements, changes (highlights):

• various display fixes
• update for nltk 3+
• documentation / notebook fixes
• improvements to packaging

[0.6.2] - Bugfix update - 2016-02-13

• packaging improvements and fixes

[0.6.1] - Bugfix update - 2016-02-07

• fix a fragment notebook

[0.6] - Polymorphism - 2016-02-07

New features:

• Support for polymorphic types and inference via type variables
• Corresponding metalanguage updates

Fixes, improvements, changes (highlights):

• Improvements for IPython 3

[0.5.1] - interim release - 2015-02-09

New features:

• %te magic
• new renderers for recursive / tree-like composition displays

Fixes, improvements, changes (highlights):

• improvements to rich reprs
• fixes to reduction

[0.5] - First public release - 2014-10-06

This version was aiming at basic intro to semantics feature completeness:

• the lambda notebook IPython kernel
• types for a simply-typed lambda calculus
• a matching more-or-less complete metalanguage for simply-typed lambda calculus
• composition systems, rich repr rendering, integration with nltk Tree
• various demo and fragment notebooks
• packaging (now completely deprecated)

(Version control begins 2014-01-01.)