changes.md

3.51.1c (24 May 2023)

Fixes:

• Fix emscripten build for web editor (#808)

3.51.0c (17 May 2023)

Fixes:

• Propagate tags through unfreezingI (#804)
• Avoid an expensive copy in simp (#801)

Changes:

• Update emscripten (#805, #806)

3.50.3c (26 December 2022)

Fixes:

• tlean expression numbering (#799)

3.50.2c (23 December 2022)

Fixes:

• Report tlean export errors (#796)
• tlean export for local constants and mvars (#797)

3.50.1c (21 December 2022)

Fixes:

• Revert (#788): put auto-bound universes before explicit (#794)

3.50.0c (12 December 2022)

Fixes:

• Push null using_well_founded AST node after := (#787)
• Use Ubuntu 20.04 for CI (#792)

Features:

• Export user attribute data in tlean files (#790)

Changes:

• Put auto-bound universes before explicit (#788)

3.49.1c (18 November 2022)

Fixes:

• Correct binder links in pp.links (#781)
• Convert /- comments to /-- or /-! comments (#782)
• Give explicit names to declaration constructor arguments (#783)
• Export using_well_founded AST node (#784)

3.49.0c (11 November 2022)

Features:

• Extend pp.links to support Pi, Prop, Type, and Sort (#778)

Fixes:

• Markdown syntax in docstring (#766)
• Name arguments in expr constructors (#773)

Changes:

• Remove unused theorems (#774)
• Backport Lean 4 definitions of min/max (#779)

3.48.0c (30 August 2022)

Changes:

• Make fin a structure (#761)

3.47.0c (25 August 2022)

Features:

• notation (name := ...) syntax (#754, #758, #759)
• Remove an unnecessary case split from or.by_cases (#755)
• Store command end position in AST (#756)
• Backport Lean 4 field notation (#757)

3.46.0c (8 August 2022)

Features:

• Add docstrings for algebra classes (#747)

Bug fixes:

• Add recursion guard in tlean exporter (#752)

Changes:

• Remove redundant assumption from is_strict_total_order (#746)

3.45.0c (27 June 2022)

Bug fixes:

• End position information sent by the lean server used for command annotations no longer includes trailing whitespace and comments (#744)
• json.parse no longer parses -1 as 4294967295, along with various other problems with integers (#743)
• native.float.of_nat, native.float.of_int, native.float.floor, native.float.ceil, native.float.round, and native.float.trunc no longer truncate to 32 bits of range (#742)
• environment.is_structure is now true on structures with no fields (#739)

Changes:

• native.float.floor, native.float.ceil, native.float.round, and native.float.trunc now return 0 on infinite inputs (#742)

3.44.1c (27 June 2022)

Changes:

• Do not treat iff refl lemmas as if they were eq refl lemmas (#736)

3.44.0c (24 June 2022)

Features:

• Add a debug configuration for vscode (#726)
• Add a docstring for reflected.subst (#729)
• Record symbol kinds in auto-completion info (#727)
• Add support for listing symbols in a file in vscode (#724)
• io.unsafe_perform_io (#730)
• Use lemmas proved with iff.rfl as refl lemmas in dsimp (#723)

Changes:

• Turn implicit arguments to ↔ in nat lemmas (#719)
• Reject Sort and suggest Prop (#732)
• Make the type argument to reflected explicit (#734)

3.43.0c (18 May 2022)

Features:

• Teach well_founded_tactics.default_dec_tac that n < n.succ (#710)
• Improve docs for acc, well_founded (#715)

Bug fixes:

• Add modifiers/attrs/docstring check to local command (#711)
• noncomputable: better error message for non-Prop theorems (#712)
• Uninstance order decidability (#714)

Changes:

• Remove tc (#713)
• Drop set.sUnion (#675)

3.42.0c (24 March 2022)

Features:

• Export pretty-printed tactic states (#702)

Bug fixes:

• Make async aware of instance cache (#706)

3.42.0c (18 March 2022)

Features:

• noncomputable! to force noncomputability (#703)
• Require non-Prop theorems to be noncomputable (#704)

Bug fixes:

• Do not use file name for private name generation (#699)
• Use 64-bit hashes for file contents (#700)

3.41.0c (11 March 2022)

Features:

• Give sorry tactic ignored itactic block (#689)
• Add pp.numeral_types option to display type ascriptions for numerals (#691)
• Add pp.numerals option to control pretty printing of unary nats (#692)
• Premise selection (#696)

Bug fixes:

• rw: move LHS metavar check (#690)
• noncomputable: for constructors, only check arguments after inductive type's parameters (#693)
• Give the heuristic instance name awareness of anonymous fields (#694)
• elim_match: better error message (#697)

3.40.0c (22 February 2022)

Bug fixes:

• Strip spaces in heuristic name for notations (#687)
• Don't skip remainder in rw_hyp (#686)

3.39.2c (17 February 2022)

Bug fixes:

• Regression in ast constant names export (#683)
• pp_tagged output for have statements (#682)

3.39.1c (8 February 2022)

Features:

• Record comments in ast (#679)

3.39.0c (3 February 2022)

Features:

• Add option pp.parens to force parentheses for notation (#669)
• lstlean.tex: ϖ and ᵒ (#671)
• pexpr is inhabited too (#674)
• id_tag for "tagging" tactic proofs (#670)
• Export ast field info for <local>.<field> (#677)

Bug fixes:

• Add missing parser_desc combinators (#676)

3.38.0c (11 January 2022)

Features:

• Import unfreezing tactic from mathlib (#667)

Changes:

• Do not check for subsingleton in simp congrs (#665)

Bug fixes:

• Allow cloning tactic states with references (#666)

3.37.0c (7 January 2021)

Features:

• Improve out_param support in simp (#659)

Bug fixes:

• More robust check in cast removal in simp (#661)
• Sort level parameters after collection (#662)
• Use vm environment in trace_widget (#663)

Changes:

• Make type argument of default implicit (#660)

3.36.0c (4 January 2021)

Bug fixes:

• Don't re-resolve calc constants (#652, fixes #651)
• Unfold recursive arguments in inductives as semireducible (#653)
• Use always_assert in drec construction (#654)
• Don't block on metavariables that depend on an out_param (#657)

Changes:

• Use }} in format strings (#650)
• Change binder collection order in ∀ (x y < n), true (#656)

3.35.1c (8 November 2021)

Features:

• Support freebsd (#643)

Bug fixes:

• Check that arguments to set_goals are mvars (#642)
• Turn comment into docstring (#646)
• Use less memory in tlean export (#648)

3.35.0c (28 October 2021)

Features:

• Add vm_decl.noncomputable_reason (#638)

Bug fixes:

• Bugfix AST export (#634)

Changes:

• Adjust universe levels of coercions to match Lean 4 (#632)
• Reorder sections in data/nat/lemmas (#635)
• Remove library/data/stream (will be moved to mathlib) (#636)
• Remove library/data/rbtree and library/data/rbmap (will be moved to mathlib) (#637)

3.34.0c (20 October 2021)

Features:

• Improve by_contradiction (#622)
• Export tleans in parallel (#627)
• Builds for Linux/aarch64 (#630)

Bug fixes:

• Fix lift_list (#626)

Changes:

• Drop prod.has_lt (#620)
• Resolve open like def (#619)
• add_decl adds parent namespaces (#618)
• Backport has_coe_to_sort/has_coe_to_fun from Lean 4 (#557)

3.33.0c (13 September 2021)

Features:

• Allow sorry macro to textualize (#602)
• AST tracking and export (#608)
• Add end-pos support to scanner (#612)
• Log tactic invocations in AST (#614)

Bug fixes:

• Make injective semireducible (#604)
• Fix compilation on MacOS 10.14 (#606)
• Fix elan override instructions (#605)
• Replace leanprover with leanprover-community in release build instructions (#610)
• Make fun_setoid instance local and not private (#611)
• Rename int.sub_one_le_of_lt and int.lt_of_sub_one_le (#616)

Changes:

• add max / min fields to linear_order (#609, fixup #615)

3.32.1c (12 August 2021)

Changes:

• Remove unification hint add_succ_defeq_succ_add_hint (#598)

3.32.0c (10 August 2021)

Features:

• Update Windows build instructions (#593)
• lift_pi_range (#590)
• Export self_opt flag in tlean files (#596)
• Let macros textualize in tleans rather than unfold (#595)

Changes:

• Protect more lemmas (#589)
• Use names self and motive in recursors (#594)
• Remove uses of export A (hiding B) in the core library (#597)
• Remove uses of reserve notation (#599)

3.31.0c (29 June 2021)

Features:

• apply: produce a better error for missing typeclasses (#577)

Bug fixes:

• Spelling (#573)
• cases: fix segfault with equalities of subtypes (#580)
• cc: partly disable broken support for symmetric relations (#579)
• Make trace thread-safe (#583)
• simp: fix segfault with ← and custom relation (#587)

Changes:

• Make exists.intro a def again (#582)
• Delete lazy_list (#581)

3.30.0c (30 April 2021)

Features:

• Add a brief docstring about unbundled classes (#568)
• Add timing info to verbose output for leanchecker (#567)
• Add docstring for nat.find (#566)

Bug fixes:

• Bug with custom recursors on add_monoid_algebra (#569)

Changes:

• Avoid well-founded recursion in nat.mod and nat.div (#570)

3.29.0c (19 April 2021)

Features:

• leanchecker: add -v flag to print declaration names (#564)
• #print universe parameters of declarations (#558)

Bug fixes:

• Fix let with coe_sort (#555)

Changes:

• acc.rec should not aggressively reduce proof (#562)
• Use name self for argument in structure projections (#561)
• Reduce use of choice (#560)

3.28.0c (15 March 2021)

Features:

• leanchecker prints error messages (#548)
• _root_ can now be used to put declarations in the root namespace (#550)

Bug fixes:

• line wrapping in to_raw_fmt (#549)
• The widget.html.to_string_coe instance now uses has_coe_t (#544)
• Fix in mt_task_queue (#552)

Changes:

• propagate_tags can now be used interactively (#540)
• Change fin.sub to the Lean 4 definition (#541)
• Some lint fixes (#545)
• Update installation instructions (#547)

3.27.0c (25 February 2021)

Features:

• Export textual .tlean files (#524)
• Allow case to match multiple cases (#508)
• specialize puts goals from underscores first (#530)
• Make has_mul.mul a pattern (#532)
• Do not clear simp cache unnecessarily (#537)
• Allow irreducible instances (#538)

Bug fixes:

• Do not treat empty JSON objects as null (#534)
• Accidentally quadratic name creation (#535)

Changes:

• Generalize exists_unique_of_exists_of_unique to sort (#526)
• Sync ite and dite with lean4 (#531)

3.26.0c (26 January 2021)

Bug fixes:

• Fix addressing bug in pretty printer (#520)

3.25.0c (21 January 2021)

Features:

• try_for_time interruption function (#517)
• Add primitives for GPT integration (#510)
• Record simplification lemmas and export them to tactic.simplify (#497)

Bug fixes:

• Correct minor typo in docstring (#518)

3.24.0c (4 January 2021)

Features:

• Position argument with insert_text (#501)
• Check that classes are types (#502)
• Enable type class cache in nested resolution problems (#505)

Bug fixes:

• Tests on arm64 (#498)
• Make infer_instance work on sorts (#506)
• Fix universe levels in punit lemmas (#507)
• Ensure json.parse/json.unparse are inverses (#509)

Changes:

• Improve default termination measure for mutually recursive functions (#496)
• Make is_lawful_singleton a Prop (#499)
• well_founded.recursion is a definition now (#503)

3.23.0c (29 October 2020)

Features:

• Expose kabstract in type_context to the VM (#391)
• Add position information to declarations added in user commands (#488)

Bug fixes:

• The a bug is replaced by the ᾰ bug (#490)

Changes:

• New instance naming heuristic (#458, #493)
• by_contradiction uses classical logic and the name h (#491)

3.22.0c (27 October 2020)

Features:

• Improve error handling of for and find in conv mode (#482, #485)

Bug fixes:

• Fix typos in docstrings for tactic.focus and tactic.focus' (#483)

Changes:

• Remove lean --doc (which never actually did anything) (#480)
• Add decidable_* assumptions to linear_order and remove decidable_linear_order (#484)

3.21.0c (12 October 2020)

Features:

• Simplify definition of band and bor (#466)
• More advice in docstrings for Exists, not, and, and or (#296)

Bug fixes:

• Fix typo in docstring for tactic.exact (#472)
• Fix missing code block in widget server docs (#473)

Changes:

• Remove global notation for vector.cons (#471)

3.20.0c (9 September 2020)

Features:

• Options are refreshed when the simplifier is entered. (#456)
• JSON support for widgets (#453)
• More definition and theorem docstrings (#463)

Bug fixes:

• Typeclass args for monad_state_trans were flipped. (#461)
• resolve_constant now handles parameters correctly. (#462)

Changes:

• Remove nat.pow from the core library (#457)

3.19.0c (27 August 2020)

Features:

• There is a new option extends_priority which controls the priority of instances produced by extends. It is set to 100 by default. (#440)
• Add docs for the Lean server API (#443)

Bug fixes:

• Fix name generation by injection_with (#430)
• Fix bug in in_current_file (#432)
• Fix docstring in introv (#434)
• Fix parse precedence for #html (#444)
• Add \fl and \fr to lstlean.tex (#448)

Changes:

• Avoid classical.choice in lt_of_le_of_ne (#428)
• Remove usage of the axiom of choice from basic nat and int lemmas, remove private from internal lemmas about int and move the decidable.* order theorems from mathlib (#446)
• Change syntax of guard_hyp from guard_hyp h := t to guard_hyp h : t and support guard_hyp h : t := val for checking let bindings (#445, #449)
• Make fin a subtype (#452)

3.18.4c (30 July 2020)

Features:

• Ensure @max (order_dual α) = @min α (#425)

Bug fixes:

• Description for small_nat (#424)
• More set replacement fixes (#426, fixes #422 and #423)

3.18.3c (29 July 2020)

Features:

• Show VM overrides in info request (#417)

Bug fixes:

• Support {(1 : α)} and {(∘), (∘)} (#420, fixes #419 and #418)

3.18.2c (28 July 2020)

Bug fixes:

• Fix {(0,1)} (#415)

3.18.1c (28 July 2020)

Bug fixes:

• Update local instances (#412, fixes #411)

3.18.0c (28 July 2020)

Features:

• Notation for set replacement (#402)

Bug fixes:

• Drop non-local-constant exprs from cases output (#390)
• Freeze local instances for definition parameters (#403, fixes #397)
• Freeze local instances in #check (#404, fixes #398)
• Honor as_is attribute for functions (#399)
• Fix VM environment issue (#405)
• Remove tactic.norm_num (#406)
• Fix injection introducing too many hyps (#407, fixes #400)
• Handle corner cases in by_cases (#409)

Changes:

• Use a structure for well_founded (#408)

3.17.1c (8 July 2020)

Features:

• Reuse type-class cache (#383)

Bug fixes:

• Info error for commands directly after imports (#386, fixes #382)

3.17.0c (6 July 2020)

Features:

• Refactor widgets to use hooks (#363, #369)
• component.with_effects (#370)
• Add "copy text" effect. (#375)

Bug fixes:

• Add margin to local const names in tactic state (#365)
• Prevent segfault in apply (#373, fixes #372)
• Fix address incorrect issue in pp_tagged (#371)
• Abort if no input consumed in module_parser (#377, fixes #374)
• Do not unify (1 : ℕ) with (1 : ℤ) (#376, fixes #362)

Changes:

• Fix vacuous assumptions in nat lemmas (#366)
• Remove has_neg instance for set (#367)
• Mark dif_ctx_congr as @[congr] (#378)

Server protocol changes:

• The response of the widget_event request may now contain effects.

3.16.5c (25 June 2020)

Features:

• Add comment-like string blocks (#352)
• Add widgets to trace messages (#355)
• Show case tags in goal widget (#357)

Bug fixes:

• Handle exceptions in ts_clone (#350)
• Support sorry # (#356)

Server protocol changes:

• The (Lean error) messages returned by the server may now contain an additional "widget" field.

3.16.4c (22 June 2020)

Features:

• Use tactic_state_context_cache more (#347)
• Goal widget: collect locals with the same type and local filtering (#346)

Bug fixes:

• Fix error message in cases

3.16.3c (18 June 2020)

Bug fixes:

• Remove as-is annotations (#338, fixes #334)
• Handle EOF in skip_to_pos (#342, fixes #85)
• Fix holes with space in name (#343)

Features:

• Add profiling for user attributes (#328)
• Profile user commands (#329)
• Support lean --profile --run (#337)
• Add parser.{any_char,digit,nat} (#331)
• Cache type-class searches w/o mvars (#332)

Changes:

• Put is_strict_total_order in Prop (#327)
• Remove redundant lemmas (#321)

3.16.2c (12 June 2020)

Bug fixes:

• Stop scanning after #exit (#318, fixes #309)
• Allow variables (A B : Type*) (#319, fixes #29)
• Escape names using French quotes by default (#320, fixes #114)
• Fix lean --deps (#323)
• Selection disco issue in tactic state widget (#324)

Features:

• Add get_widget server request (#314)
• Allow namespaces inside sections (#317, fixes #315)

Server protocol changes:

• The info request no longer returns the widget HTML. Instead it returns an id field in addition to line and column. The get_widget request now returns the HTML. The widget_event request also requires an id argument.

3.16.1c (10 June 2020)

Bug fixes:

• Add key to li in tactic_view_component (#311)
• Fix widget updates in by ... (#312)

3.16.0c (10 June 2020)

Features:

• Add docstrings for cc_state primitives (#295)
• Use BUILD_TESTING to enable or disable building tests (#292)
• Additional meta constants (#294)
• Add @[pp_nodot] (#297)
• Make widget look more like current tactic state (#303)
• Show term-proof goals as widgets (#304, #306)
• Add holes for underscores (#307)

Bug fixes:

• Fix case of header files for building on case-sensitive filesystems (#290)
• Remove useless setting of _GLIBCXX_USE_CXX11_ABI with MinGW (#293)
• Fix guards to make it possible to build for BSD systems (#291)
• Rename tactic.tactic.run_simple -> tactic.run_simple (#298)
• Use instance instead of semireducible transparency in type-class synthesis (#300)
• Widget events contain position (#301)
• Server: do not cancel info queries, etc. (#308)

Changes:

• Lower precedence of unary - (#287)

3.15.0c (28 May 2020)

Features:

• Support for structured formatting using eformat (#276)
• Show goals for subterms (#275, #277)
• Freeze instances in the simplifier (#273)
• Support local attribute with docstring (#271)
• VM objects may be hashed (#262)
• expr.coord and expr.address (#260)
• Add list.map_with_index to core library (#259)
• Add expr.instantiate_vars_core (#261)
• Don't check levels on meta inductives (#263)

Bug fixes:

• Preserve VM code indexes across instances (#283)
• Fixes a VM environment cache not updating (#280)
• Do not use fseek in io.fs.read (#278)
• Dot-notation pretty-printing (#269)

Changes:

• Elaborate structure instances left-to-right (#282)
• Remove duplicated namespaces (#267)
• Remove (| and |) aliases (#265)

Special feature: widgets

Lean API

• Add widgets. This is an HTML-based UI framework for generating html within lean to enable interactive UI in the infoview in vscode and on the web.
• Add tactic.save_widget: pos → widget.component tactic_state string → tactic unit. Examples of widgets can be found in library/widget/examples.lean. Widgets are registered in exactly the same way as save_info_thunk saves text.
• Use the #html command to view html empty or component tactic_state string widgets.
• Add a 'structured format' pretty printing system tactic_state.pp_tagged : tactic_state → expr → eformat. eformat := tagged_format (expr.address × expr). tagged_format α : Type performs the same role as format except that there is a special constructor tag : α → tagged_format → tagged_format that contains information about which subexpression caused this string to be rendered. This is used to implement a widget which allows the user to hover over a pretty printed string and view information about the subexpressions that build up the original expression. For example, this lets you view types of pretty printed expressions and view implicit arguments.
• Add numerous docstrings

Frontend/library changes

• Overhaul pretty printer so that it can provide information about expression addresses. This required making it templated to output T instead of format. Currently T may be instantiated with lean::format or lean::eformat. See src/library/vm/vm_eformat and
• Info manager now supports widgets.
• Server info response may now include a "widget" field on the returned "record" json.
• Server has a new command widget_event to enable interactive widgets
• The main code for widgets can be found in src/frontends/widget.(h|cpp).
• VM objects can now be hashed, with the exception of some vm_externals which hash to zero. This is needed to verify the identity of components in the widget reconciliation engine.
• server has an option -no-widgets or -W for turning off widget reporting. This is used in the interactive tests.

v3.14.0c (20 May 2020)

Features:

• Coercions also trigger if the types have metavariables (#251)
• Better error message on missing imports (#253)
• Add add_eqn_lemma function (#254)

v3.13.2c (18 May 2020)

Fixes:

• Fix olean_doc_strings (#249)

v3.13.1c (17 May 2020)

Fixes:

• Protect and rename some nat and int lemmas that are superseded in mathlib (#229)

v3.13.0c (16 May 2020)

Features:

• use persistent data structures, to improve performance of (module) docstrings (#241)
• cache constructed simp_lemma objects (#234)
• support local attribute [-instance] (#240)
• show goal after ; (#239)
• ==: compare id (#238)
• mark deps of fixed as fixed (#237)

Changes:

• Most of library/init/algebra/* has been deleted, as part of moving the algebraic hierarchy to mathlib (#229)

v3.12.0c (14 May 2020)

Features:

• Tactic combinators with informative results (#212)
• has_singleton is a new typeclass (#217)
• Add instances for has_repr name, has_repr case_tag, and has_to_format case_tag (#230)

Changes:

• library/init/function: use dot notation, add some docstrings (#216)
• tactic.all_goals is now called tactic.all_goals', etc. (#212)
• norm_num is removed (#224)
• Parse {a,b,c} as right associative (#153)
• Refactor case tags (#228)
• Enable pp.generalized_field_notation by default (#227)

v3.11.0c (8 May 2020)

Feature:

• Do not unfold irreducible definitions in unification (#211)
• Instantiate metavariables in rw (#213)

Bug fixes:

• Fix docstring of tactic.interactive.rename (#210)

v3.10.0c (2 May 2020)

Features:

• by calc ... is now equivalent to by refine calc ... (#203)
• Flag to use out-of-date oleans (#208)
• Order notation by priority in pretty-printer (#207)
• Improve congruence lemmas for coe_fn (#209)
• Port rename tactic from mathlib (#205)

Bug fixes:

• simp [← foo] avoids looping if foo is already in the simp set (#198)

Changes:

• init.category has been renamed to init.control (#202)
• string.has_decidable_eq is now implemented by foot (#204)

v3.9.0c (19 April 2020)

Features:

• The VM supports string literals (#185, #187)
• Imports are parsed in an indentation-sensitive way. Compare:

  import foo
    bar
  open_locale classical -- runs user command

  and

  import foo
    bar
    open_locale classical -- imports open_locale and classical modules

  This makes it easier to run user commands at the start of files. (#188)
• The parser now has access to the local scope and can parse expressions as patterns (#192)
• mmap and map functions for d_array, array, and buffer (#190)

Bug fixes:

• The order of emetas has been reversed in simp_lemmas (#183)
• Universe parameters are collected from anonymous instances (#189)
• Nested comment parsing in doc strings was fixed (#191)

Changes:

• The performance of array.map has been greatly improved (#186)
• A frequently-violated assertion was removed from the elaborator (#194)

v3.8.0c (9 April 2020)

Features:

• The VM implementation of functions can be overriden (#48)
• More and better doc strings for the core library (#166)

Bug fixes:

• simp instantiates the metavariables in the goal before simplifying (#170)
• app_builder is more robust (#165)
• Assertion violation in simp_inductive (#173)

Changes:

• expr.subst constructs an application if the left expression is not a lambda (#180)
• if_simp_congr is removed, simp now produces the correct decidability instance when simplifying if-then-else (#159)
• float.{ceil,floor,trunc,round} now return integers (#176)
• default is now an export (#161)
• prod.map and function.uncurry don't use pattern matching (#161)
• The type argument in has_zero.zero and has_one.one is implicit (#169)
• Inductives/structures/structure fields now default to implicit arguments (#175)
• add_lt_add_left and mul_le_mul* fields are removed (#167)
• ordered_comm_group is renamed to ordered_add_comm_group (#174)

v3.7.2c (20 Mar 2020)

Bug fix:

• Open .oleans in binary mode on Windows (#155)

v3.7.1c (16 Mar 2020)

Bug fix:

• Allow loading standalone .olean files (#150)

v3.7.0c (13 Mar 2020)

Features:

• simp can rewrite subsingletons (#134)
• Files are recompiled based on hash code instead of timestamp (#140)
• mk_protected, add_protected, is_protected functions (#138)
• has_attribute and copy_attribute now expliclity support non-persistent attributes (#66)

Bug fixes:

• Fix the implementation of the instance has_coe (tactic α) (parser α) (#136 and #147)
• simp catches exception (e.g. from type class resolution, #142)
• (+) = (λ x y, x + y) unifies now (#141)

Changes:

• apply solves instances in forward order (#67)
• Type class resolution solves instance arguments from right-to-left (#139)
• Type class resolution skips assigned metavariables (#135)
• Signature of has_attribute and copy_attribute has changed (#66)

v3.6.1c (2 Mar 2020)

Bug fix:

• Correctly reference the community fork of Lean in leanpkg.toml (#131)

v3.6.0c (26 Feb 2020)

Features:

• Remove discrete_field (#119)
• Remove simp attribute from sub_eq_add_neg (#117)
• Replace insert definition by export (#115)
• Remove simp attribute from add_comm and add_left_comm (#65)
• simp with reversed lemmas: simp ← foo (#100)
• Allow nested block comments in docstrings (#113)

Bug fixes:

• Include mathlib fixes to wf_tacs (#121)
• Typos in docstrings (#125)

Changes:

• discrete_field is now just field (#119)
• add_comm, add_left_comm, and sub_eq_add_neg are no longer simp lemmas
• insert is no longer a definition
• Nested block comments are now allowed in docstrings

v3.5.1c (4 Feb 2020)

Features:

• Allow change to be used to rename bound variables (#96)
• Annotate pretty-printed output with full constant names (#89)
• Import modules from meta code (#88)
• Make add_interactive copy the doc string (#97)
• Avoid version warning for external Leans in leanpkg (#106)

Bugfixes:

• Force tactic type in run_cmd (#103)
• ?m_1 and (λ x, ?m_1) y should be definitionally equal (#107)

v3.5.0c (26 Dec 2019)

This is the first community release of Lean 3.

Features

• Add native.float for using floating point values within meta functions.

• Add reflect (p : parser α) [r : reflectable p] : parser expr def for parsing raw exprs. (#33)

• Add tactic.unsafe.type_context and local_context for directly interacting with Lean's type context.

  This means that metavariables and local constants can be directly declared and assigned. (#69)

• Docstrings are now supported on inductive constructors. (#61)

• Add environment.add_defn_eqns to programmatically create a definition that uses the equation compiler. (#26)

• Add environment.add_ginductive to give tactics access to the utility lemmas associated with inductive type declaration. (#3)

• Improve file API. Add support for UNIX sockets. (#20, #31)

• Add lean.parser.itactic, a tactic block parser. (#19)

• Add interactive.executor, a class to implement custom tactic monads in begin ... end blocks. (#10)

• Add expr serialization/deserialization functions. (#6)

• Improve and add numerous docstrings.

• Module documentation is now stored in .olean files to allow documentation to be automatically generated. (#54)

• Documentation of all imported modules is now exposed via the olean_doc_strings tactic. (#81)

Bug Fixes

• build: fix emscripten build in travis (#68)
• CMakeLists.txt: GCC 9.1.0 miscompiles certain if statements #63
• tactic/revert_tactic: disallow duplicates (#56)
• level: give level.instantiate correct type (#46)
• documentation: The closing code fence must match opening fence. (#40)
• emscripten: fix FS issue: don't mkdir in docker (#39)
• emscripten: fix emscripten build (#17)
• tactic/case: case fails when used with let (#32)
• tactic/revert_lst: check that the provided expressions are variables (#12)
• tactic/type_check: do not assign to meta variables (#86)
• init/algebra/field: repeated instance (#8)
• Add an additional check to type_context_old::mk_class_instance_at(lctx,type) to fix issue #55. (#79)

Changes

• Notation removed: =<<, >=>, <=<
• transfer and relator namespaces removed.

v3.4.2 (18 Jan 2019)

Patch release

Features

• leanpkg: Allow specifying a branch to use for leanpkg upgrade (#1981)

Changes

• Fix the definition of list.lt

• Make leanpkg work when installed in a path containing spaces

• io: Encode/decode UTF-8 for text-mode streams

• Remove coinductive predicates and transfer. To be moved to mathlib instead.

• Windows: Ignore file changes that only changed line endings

v3.4.1 (28 April 2018)

Bugfix release: Fix a regression concerning type ascriptions in function position

v3.4.0 (16 April 2018)

Features

• Implement RFC #1820

• Add string.iterator abstraction for traversing strings. The VM contains an efficient implementation of this type.

• Add support for non-ASCII char literals. Example: 'α'.

• Unicode escape characters in string and char literals. For example, '\u03B1' is equivalent to 'α'.

• Predictable runtime cost model for recursive functions. The equation compiler uses different techniques for converting recursive equations into recursors and/or well-founded fixed points. The new approach used in the code generator ignores these encoding tricks when producing byte code. So, the runtime cost model is identical to the one in regular strict functional languages.

• Add d_array n α (array type where value type may depend on index), where (α : fin n → Type u).

• Add instance for decidable_eq (d_array n α) and decidable_eq (array n α). The new instance is more efficient than the one in mathlib because it doesn't convert the array into a list.

• Add aliasing pattern syntax id@pat, which introduces the name id for the value matched by the pattern pat.

• Add alternative syntax {..., ..s} for the structure update {s with ...}. Multiple fallback sources can be given: {..., ..s, ..t} will fall back to searching a field in s, then in t. The last component can also be .., which will replace any missing fields with a placeholder. The old notation will be removed in the future.

• Add support for structure instance notation {...} in patterns. Use .. to ignore unmatched fields.

• Type class has_equiv for ≈ notation.

• Add funext ids* tactic for applying the funext lemma.

• Add iterate n { t } for applying tactic t n times. Remark: iterate { t } applies t until it fails.

• Add with_cases { t }. This tactic applies t to the main goal, and reverts any new hypothesis in the resulting subgoals. with_cases also enable "goal tagging". Remark: induction and cases tag goals using constructor names. apply and constructor tag goals using parameter names. The case tactic can select goals using tags.

• Add cases_matching p tactic for applying the cases tactic to a hypothesis h : t s.t. t matches the pattern p. Alternative versions: cases_matching* p and cases_matching [p_1, ..., p_n]. Example: cases_matching* [_ ∨ _, _ ∧ _] destructs all conjunctions and disjunctions in the main goal.

• Add cases_type I tactic for applying the cases tactic to a hypothesis h : I .... cases_type! I only succeeds when the number of resulting goals is <= 1. Alternative versions: cases_type I_1 ... I_n, cases_type* I, cases_type!* I. Example: cases_type* and or destructs all conjunctions and disjunctions in the main goal.

• Add constructor_matching p tactic. It is syntax sugar for match_target p; constructor. The variant constructor_matching* p is more efficient than focus1 { repeat { match_target p; constructor } } because the patterns are compiled only once.

• injection h now supports nested and mutually recursive datatypes.

• Display number of goals in the *Lean Goal* buffer (if number of goals > 1).

• hide id* command for hiding aliases. The following command hides the alias is_true for decidable.is_true.

  hide is_true
  

• Add abbreviation declaration command. abbreviation d : t := v is equivalent to @[reducible, inline] def d : t := v and a kernel reducibility hint. Before this command, we had to use meta programming for setting the kernel reducibility hint. This was problematic because we could only define abbreviations after the meta programming framework was defined.

• Add "smart unfolding". The idea is to prevent internal compilation details used by the equation compiler to "leak" during unification, tactic execution and reduction. With "smart unfolding", the term nat.add a (nat.succ b) reduces to nat.succ (nat.add a b) instead of nat.succ (... incomprehensible mess ...). This feature addresses a problem reported by many users. See issue #1794. The command set_option type_context.smart_unfolding false disables this feature.

• Add support for "auto params" at simp tactic. Example: given

  @[simp] lemma fprop1 (x : nat) (h : x > 0 . tactic.assumption) : f x = x := ...
  

  The simplifier will try to use tactic assumption to synthesize parameter h.

• Add interactive sorry tactic (alias for admit).

• simp now reduces equalities c_1 ... = c_2 ... to false if c_1 and c_2 are distinct constructors. This feature can be disabled using simp {constructor_eq := ff}.

• simp now reduces equalities c a_1 ... a_n = c b_1 ... b_n to a_1 = b_1 /\ ... /\ a_n = b_n if c is a constructor. This feature can be disabled using simp {constructor_eq := ff}.

• subst and subst_vars now support heterogeneous equalities that are actually homogeneous (i.e., @heq α a β b where α and β are definitionally equal).

• Add interactive subst_vars tactic.

• Add leanpkg add foo/bar as a shorthand for leanpkg add https://github.com/foo/bar.

• Add leanpkg help <command>.

• Add [norm] simp set. It contains all lemmas tagged with [simp] plus any lemma tagged with [norm]. These rules are used to produce normal forms and/or reduce the number of constants used in a goal. For example, we plan to add the lemma f <$> x = x >>= pure ∘ f to [norm].

• Add iota_eqn : bool field to simp_config. simp {iota_eqn := tt} uses all non trivial equation lemmas generated by equation/pattern-matching compiler. A lemma is considered non trivial if it is not of the form forall x_1 ... x_n, f x_1 ... x_n = t and a proof by reflexivity. simp! is a shorthand for simp {iota_eqn := tt}. For example, given the goal ... |- [1,2].map nat.succ = t, simp! reduces the left-hand-side of the equation to [nat.succ 1, nat.succ 2]. In this example, simp! is equivalent to simp [list.map].

• Allow the Script, Double-struck, and Fractur symbols from Mathematical Alphanumeric Symbols: https://unicode.org/charts/PDF/U1D400.pdf to be used as variables Example: variables 𝓞 : Prop.

• Structure instance notation now allows explicitly setting implicit structure fields

• Structure instance notation now falls back to type inference for inferring the value of a superclass. This change eliminates the need for most .. source specifiers in instance declarations.

• The --profile flag will now print cumulative profiling times at the end of execution

• do notation now uses the top-level, overloadable bind function instead of has_bind.bind, allowing binds with different type signatures

• Structures fields can now be defined with an implicitness infer annotation and parameters.

  class has_pure (f : Type u → Type v) :=
  -- make f implicit
  (pure {} {α : Type u} : α → f α)
  

• Add except_t and reader_t monad transformers

• Add monad_{except,reader,state} classes for accessing effects anywhere in a monad stack without the need for explicit lifting. Add analogous monad_{except,reader,state}_adapter classes for translating a monad stack into another one with the same shape but different parameter types.

Changes

• Command variable [io.interface] is not needed anymore to use the io monad. It is also easier to add new io primitives.

• Replace inout modifier in type class declarations with out_param modifier. Reason: counterintuitive behavior in the type class resolution procedure. The result could depend on partial information available in the inout parameter. Now a parameter (R : inout α → β → Prop) should be written as (R : out_param (α → β → Prop)) or (R : out_param $ α → β → Prop). Remark: users may define their own notation for declaring out_params. Example:

  notation `out`:1024 a:0 := out_param a
  

  We did not include this notation in core lib because out is frequently used to name parameters, local variables, etc.

• case tactic now supports the with_cases { t } tactic. See entry above about with_cases. The tag and new hypotheses are now separated with :. Example:

  • case pos { t }: execute tactic t to goal tagged pos
  • case pos neg { t }: execute tactic t to goal tagged pos neg
  • case : x y { t }: execute tactic t to main goal after renaming the first two hypotheses produced by preceding with_case { t' }.
  • case pos neg : x y { t } : execute tactic t to goal tagged pos neg after renaming the first two hypotheses produced by preceding with_case { t' }.

• cases h now also tries to clear h when performing dependent elimination.

• repeat { t } behavior changed. Now, it applies t to each goal. If the application succeeds, the tactic is applied recursively to all the generated subgoals until it eventually fails. The recursion stops in a subgoal when the tactic has failed to make progress. The previous repeat tactic was renamed to iterate.

• The automatically generated recursor C.rec for an inductive datatype now uses ih to name induction hypotheses instead of ih_1 if there is only one. If there is more than one induction hypotheses, the name is generated by concatenating ih_ before the constructor field name. For example, for the constructor

  | node (left right : tree) (val : A) : tree
  

  The induction hypotheses are now named: ih_left and ih_right. This change only affects tactical proofs where explicit names are not provided to induction and cases tactics.

• induction h and cases h tactic use a new approach for naming new hypotheses. If names are not provided by the user, these tactics will create a "base" name by concatenating the input hypothesis name with the constructor field name. If there is only one field, the tactic simply reuses the hypothesis name. The final name is generated by making sure the "base" name is unique. Remarks:

  • If h is not a hypothesis, then no concatenation is performed.
  • The old behavior can be obtained by using the following command

  set_option tactic.induction.concat_names false
  

  This change was suggested by Tahina Ramananandro. The idea is to have more robust tactic scripts when helper tactics that destruct many hypotheses automatically are used. Remark: The new guard_names { t } tactical can be used to generate robust tactic scripts that are not sensitive to naming generation strategies used by t.

• Remove [simp] attribute from lemmas or.assoc, or.comm, or.left_comm, and.assoc, and.comm, and.left_comm, add_assoc, add_comm, add_left_com, mul_assoc, mul_comm and mul_left_comm. These lemmas were being used to "sort" arguments of AC operators: and, or, (+) and (*). This was producing unstable proofs. The old behavior can be retrieved by using the commands local attribute [simp] ... or attribute [simp] ... in the affected files.

• string is now a list of unicode scalar values. Moreover, in the VM, strings are implemented as an UTF-8 encoded array of bytes.

• array α n is now written array n α. Motivation: consistency d_array n α.

• Move rb_map and rb_tree to the native namespace. We will later add pure Lean implementations. Use open native to port files.

• apply t behavior changed when type of t is of the form forall (a_1 : A_1) ... (a_n : A_n), ?m ..., where ?m is an unassigned metavariable. In this case, apply t behaves as apply t _ ... _ where n _ have been added, independently of the goal target type. The new behavior is useful when using apply with eliminator-like definitions.

• ginduction t with h h1 h2 is now induction h : t with h1 h2.

• apply_core now also returns the parameter name associated with new metavariables.

• apply now also returns the new metavariables (and the parameter name associated with them). Even the assigned metavariables are returned.

• by_cases p with h ==> by_cases h : p

• leanpkg now always stores .lean package files in a separate src directory.

• Structure constructor parameters representing superclasses are now marked as instance implicit. Note: Instances using the {...} structure notation should not be affected by this change.

• The monad laws have been separated into new type classes is_lawful_{functor,applicative,monad}.

• unit is now an abbreviation of punit.{0}

API name changes

• monad.has_monad_lift(_t) ~> has_monad_lift(_t)
• monad.map_comp ~> comp_map
• state(_t).{read,write} ~> {get,put} (general operations defined on any monad_state)
• deleted monad.monad_transformer
• deleted monad.lift{n}. Use f <$> a1 <*> ... <*> an instead of monad.lift{n} f a1 ... an.
• merged has_map into functor
• unit_eq(_unit) ~> punit_eq(_punit)

v3.3.0 (14 September 2017)

Features

• In addition to user-defined notation parsers introduced in Lean 3.2.0, users may now also define top-level commands in Lean. For an example, see the coinductive command that has been ported to the new model.

• Add new simplifier configuration option simp_config.single_pass. It is useful for simplification rules that may produce non-termination. Example: simp {single_pass := tt}

• The rewrite tactic has support for equational lemmas. Example: Given a definition f, rw [f] will try to rewrite the goal using the equational lemmas for f. The tactic fails if none of the equational lemmas can be used.

• Add simp * at * variant. It acts on all (non dependent propositional) hypotheses. Simplified hypotheses are automatically inserted into the simplification set as additional simplification rules.

• Add «id» notation that can be used to declare and refer to identifiers containing prohibited characters. For example, a.«b.c» is a two-part identifier with parts a and b.c.

• simp tactic now handles lemmas with metavariables. Example simp [add_comm _ b].

• conv { ... } tactic for applying simplification and rewriting steps. In the block {...}, we can use tactics from conv.interactive. Examples:

  • conv at h in (f _ _) { simp } applies simp to first subterm matching f _ _ at hypothesis h.
  • conv in (_ = _) { to_lhs, whnf } replace the left-hand-side of the equality in target with its weak-head-normal-form.
  • conv at h in (0 + _) { rw [zero_add] }
  • conv { for (f _ _) [1, 3] {rw [h]}, simp }, first execute rw[h] to the first and third occurrences of an f-application, and then execute simp.

• simp tactics in interactive mode have a new configuration parameter (discharger : tactic unit) a tactic for discharging subgoals created by the simplifier. If the tactic fails, the simplifier tries to discharge the subgoal by reducing it to true. Example: simp {discharger := assumption}.

• simp and dsimp can be used to unfold projection applications when the argument is a type class instance. Example: simp [has_add.add] will replace @has_add.add nat nat.has_add a b with nat.add a b

• dsimp has several new configuration options to control reduction (e.g., iota, beta, zeta, ...).

• Non-exhaustive pattern matches now show missing cases.

• induction e now also works on non-variable e. Unlike ginduction, it will not introduce equalities relating e to the inductive cases.

• Add notation #[a, b, c, d] for bin_tree.node (bin_tree.node (bin_tree.leaf a) (bin_tree.leaf b)) (bin_tree.node (bin_tree.leaf c) (bin_tree.leaf d)). There is a coercion from bin_tree to list. The new notation allows to input long sequences efficiently. It also prevents system stack overflows.

• Tactics that accept a location parameter, like rw thm at h, may now use ⊢ or the ASCII version |- to select the goal as well as any hypotheses, for example rw thm at h1 h2 ⊢.

• Add user_attribute.after_set/before_unset handlers that can be used for validation as well as side-effecting attributes.

• Field notation can now be used to make recursive calls.

def list.append : list α → list α → list α
| []       l := l
| (h :: s) t := h :: s.append t

• leanpkg now stores the intended Lean version in the leanpkg.toml file and reports a warning if the version does not match the installed Lean version.

• simp and dsimp can now unfold let-bindings in the local context. Use dsimp [x] or simp [x] to unfold the let-binding x : nat := 3.

• User-defined attributes can now take parameters parsed by a lean.parser. A [derive] attribute that can derive typeclasses such as decidable_eq and inhabited has been implemented on top of this.

Changes

• We now have two type classes for converting to string: has_to_string and has_repr. The has_to_string type class in v3.2.0 is roughly equivalent to has_repr. For more details, see discussion here.

• Merged assert and note tactics and renamed -> have.

• Renamed pose tactic -> let

• assume is now a real tactic that does not exit tactic mode.

• Modified apply tactic configuration object, and implemented RFC #1342. It now has support for auto_param and opt_param. The new eapply tactic only creates subgoals for non dependent premises, and it simulates the behavior of the apply tactic in version 3.2.0.

• Add configuration object rewrite_cfg to rw/rewrite tactic. It now has support for auto_param and opt_param. The new goals are ordered using the same strategies available for apply.

• All dsimp tactics fail if they did not change anything. We can simulate the v3.2.0 using dsimp {fail_if_unchaged := ff} or try dsimp.

• dsimp does not unfold reducible definitions by default anymore. Example: function.comp applications will not be unfolded by default. We should use dsimp [f] if we want to reduce a reducible definition f. Another option is to use the new configuration parameter unfold_reducible. Example dsimp {unfold_reducible := tt}

• All dunfold and unfold tactics fail if they did not unfold anything. We can simulate the v3.2.0 using unfold f {fail_if_unchaged := ff} or try {unfold f}.

• dunfold_occs was deleted, the new conv tactical should be used instead.

• unfold tactic is now implemented on top of the simp tactics. So, we can use it to unfold declarations defined using well founded recursion. The unfold1 variant does not unfold recursively, and it is shorthand for unfold f {single_pass := tt}. Remark: in v3.2.0, unfold was just an alias for the dunfold tactic.

• Deleted simph and simp_using_hs tactics. We should use simp [*] instead.

• Use simp [-h] and dsimp [-h] instead of simp without h and dsimp without h. Moreover, simp [*, -h] if h is a hypothesis, we are adding all hypotheses but h as additional simplification lemmas.

• Changed notation rw [-h] to rw [← h] to avoid confusion with the new simp [-h] notation. The ASCII version rw [<- h] is also supported.

• rw [t] at * now skips any hypothesis used by t. See discussion here.

• Removed the redundant keywords take (replace with assume) and suppose (replace with the new anonymous assume :)

• Universes max u v + 1 and imax u v + 1 are now parsed as (max u v) + 1 and (imax u v) + 1.

• Merged generalize and generalize2 tactics into new generalize id? : expr = id tactic

• standard.lean has been removed. Any files that import standard can simply remove the line as most things that were once imported by this are now imported by default.

• The type classes for orders have been refactored to combine both the (<) and (≤) operations. The new classes are preorder, partial_order, and linear_order. The partial_order class corresponds to weak_order, strict_order, order_pair, and strong_order_pair. The linear_order class corresponds to linear_order_pair, and linear_strong_order_pair.

• injection and injections tactics generate fresh names when user does not provide names. The fresh names are of the form h_<idx>. See discussion here.

• Use structure to declare and. This change allows us to use h.1 and h.2 as shorthand for h.left and h.right.

• Add attribute [pp_using_anonymous_constructor] to and. Now, and.intro h1 h2 is pretty printed as ⟨h1, h2⟩. This change is motivated by the previous one. Without it, and.intro h1 h2 would be pretty printed as {left := h1, right := h2}.

• User attributes can no longer be set with set_basic_attribute. You need to use user_attribute.set now.

• The Emacs mode has been moved into its own repository and MELPA packages: https://github.com/leanprover/lean-mode

API name changes

• list.dropn => list.drop
• list.taken => list.take
• tactic.dsimp and tactic.dsimp_core => tactic.dsimp_target
• tactic.dsimp_at_core and tactic.dsimp_at => tactic.dsimp_hyp
• tactic.delta_expr => tactic.delta
• tactic.delta => tactic.delta_target
• tactic.delta_at => tactic.delta_hyp
• tactic.simplify_goal => tactic.simp_target
• tactic.unfold_projection => tactic.unfold_proj
• tactic.unfold_projections_core => tactic.unfold_projs
• tactic.unfold_projections => tactic.unfold_projs_target
• tactic.unfold_projections_at => tactic.unfold_projs_hyp
• tactic.simp_intros_using, tactic.simph_intros_using, tactic.simp_intro_lst_using, tactic.simph_intro_lst_using => tactic.simp_intros
• tactic.simp_at => tactic.simp_hyp
• deleted tactic.simp_at_using
• deleted tactic.simph_at

v3.2.0 (18 June 2017)

Lean is still evolving rapidly, and we apologize for the resulting instabilities. The lists below summarizes some of the new features and incompatibilities with respect to release 3.1.0.

Features

• Holes {! ... !} expressions and (user-defined) hole commands. In Emacs, hole commands are executed using the keybinding C-c SPC. The available commands can be found here.

• The leanpkg package manager now manages projects and dependencies. See the documentation here. Parts of the standard library, like the superposition theorem prover super, have been moved to their own repositories. .project files are no longer needed to use emacs with projects.

• Well-founded recursion is now supported. (Details and examples for this and the next two items will soon appear in Theorem Proving in Lean.)

• Mutually (non meta) recursive definitions are now supported.

• Nested and mutual inductive data types are now supported.

• There is support for coinductive predicates.

• The simp tactic has been improved and supports more options, like wildcards. Hover over simp in an editor to see the documentation string (docstring).

• Additional interactive tactics have been added, and can be found here.

• A case tactic can now be used to structure proofs by cases and by induction. See here.

• Various data structures, such as hash maps, have been added to the standard library here.

• There is preliminary support for user-defined parser extensions. More information can be found here, and some examples can be found here.

• Numerous improvements have been made to the parallel compilation infrastructure and editor interfaces, for example, as described here and here.

• There is a transfer method that can be used to transfer results e.g. to isomorphic structures; see here.

• The monadic hierarchy now includes axioms for monadic classes. (See here.)

• The tactic notation tac ; [tac_1, ..., tac_n] has been added.

• The type classes has_well_founded, has_map, has_seq, has_orelse have been added.

• Type classes can have input/output parameters. Some examples can be found here.

• tactic.run_io can now be used to perform IO in tactics.

Changes

• Type class instances are not [reducible] by default anymore.

• Commands that produce output are now preceded by a hash symbol, as in #check, #print, #eval and #reduce. The #eval command calls the bytecode evaluator, and #reduce does definitional reduction in the kernel. Many instances of alternative syntax like premise for variable and hypothesis for parameter have been eliminated. See the discussion here.

• The hierarchy of universes is now named Sort 0, Sort 1, Sort 2, and so on. Prop is alternative syntax for Sort 0, Type is alternative syntax for Sort 1, and Type n is alternative syntax for Sort (n + 1). Many general constructors have been specialized from arbitrary Sorts to Type in order to simplify elaboration.

• Automatically generate dependent eliminators for inductive predicates.

• Improve unification hint matcher.

• Improve unifier. In function applications, explicit arguments are unified before implicit ones. Moreover, more aggresive unfolding is used when processing implicit arguments.

• Use universe u instead of universe variable u to declare a universe variable.

• The syntax l^.map f for projections is now deprecated in favor of l.map f.

• The behavior of the show tactic in interactive tactic mode has changed. It no longer leaves tactic mode. Also, it can now be used to select a goal other than the current one.

• The assertv and definev tactics have been eliminated in favor of note and pose.

• has_andthen type class is now heterogeneous,

• The encoding of structures has been changed, following the strategy described here. Generic operations like add and mul are replaced by has_add.add and has_mul.mul, respectively. One can provisionally obtain the old encodings with set_option old_structure_cmd true .

• Syntax for quotations in metaprograms has changed. The notation `(t) elaborates t at definition time and produces an expression. The notation ``(t) resolves names at definition time produces a pre-expression, and ```(t) resolves names at tactic execution time, and produces a pre-expression. Details can be found in the paper Ebner et al, A Metaprogramming Framework for Formal Verification.

• The types expr for expressions and pexpr for pre-expressions have been unified, so that pexpr is defined as expr ff. See here.

• Handling of the io monad has changed. Examples can be found here in the code for leanpkg, which is written in Lean itself.

• state and state_t are universe polymorphic.

• option_map and option_bind have been renamed to option.map and option.bind, respectively.

• GCC 7 compatibility

• Use single quotes for character literals (e.g., 'a').