1.0a1

Removals

• The core function name has been removed. Use unmangle or the name attribute of keyword objects instead.
• deftag has been removed. Instead of (deftag foo …), say (defmacro "#foo" …).
• #doc has been removed. Instead of #doc @, say (doc "#@").
• __tags__ has been removed. Tag macros are now tracked in __macros__.

Other Breaking Changes

• Lambda lists (function parameter lists) have been simplified. &optional is gone, &args is #*, &kwargs is #**, and &kwonly is *. Thus, [a &optional b [c 3] &rest args &kwargs kwargs] is now [a [b None] [c 3] #* args #** kwargs].
• Hy models have been renamed to remove "Hy", and are no longer automatically brought into scope. Thus, HyList is now hy.models.List.
• eval is no longer automatically brought into scope. Call it as hy.eval (or import it explicitly).
• Calling a keyword object now does a string lookup, instead of a keyword-object lookup. Thus, (:key obj) is equivalent to (get obj (mangle (. :key name))).
• To require a tag macro foo, instead of (require [module [foo]]), you must now say (require [module ["#foo"]]).
• Mangling no longer converts leading hyphens to underscores, and unmangling no longer converts leading underscores to hyphens.
• F-strings now have their own model type, and store their code parts as models instead of strings.

New Features

• Python 3.10 is now supported.
• Lambda lists now support positional-only arguments.
• F-strings now support = syntax per Python.
• with now supports unnamed context managers.
• defmacro and require can now take macro names as string literals.
• New standard macros do-n, list-n, and cfor.
• The location of the REPL history file can now be set with the environment variable HY_HISTORY.
• REPL initialization scripts are now supported with the envrionment variable HYSTARTUP.
• The module hy.extra.reserved has a new function special.
• New module hy.contrib.destructure for Clojure-style destructuring.
• New module hy.contrib.slicing for multi-index sequence slicing.

Bug Fixes

• Fixed the identifier J being incorrectly parsed as a complex number.
• Attempts to assign to constants are now more reliably detected.
• Fixed a bug where AST nodes from macro expansion did not properly receive source locations.
• Fixed doc sometimes failing to find core macros.
• doc now works with names that need mangling.
• Fixed bugs with require of names that need mangling.
• Fixed a compiler crash from trying to use .. as an operator.
• Fixed namespace pollution caused by automatic imports of Hy builtins and macros.
• require now works with relative imports and can name modules as members, as in (require [hy.contrib [walk]]).
• Fixed error handling for illegal macro names.
• Fixed hyc and hy2py not finding relative imports.
• Fixed hy.contrib.walk.smacrolet requiring a module name.

Misc. Improvements

• The library astor is no longer required on Pythons ≥ 3.9.

0.20.0

Removals

• Python 3.5 is no longer supported.

New Features

• let macro now supports extended iterable unpacking syntax.
• New contrib module pprint, a Hy equivalent of python.pprint.

Bug Fixes

• Fixed a bug that made hy.eval from Python fail on require.
• Fixed a bug that prevented pickling of keyword objects.
• Fixed a compiler crash from setv with an odd number of arguments in defclass.

0.19.0

Breaking Changes

• parse-args is no longer implemented with eval; so e.g. you should now say :type int instead of :type 'int.

New Features

• Python 3.9 is now supported.

Bug Fixes

• Improved support for nesting anaphoric macros by only applying symbol replacement where absolutely necessary.
• Quoted f-strings are no longer evaluated prematurely.
• Fixed a regression in the production of error messages for empty expressions.
• Fixed a scoping bug for code executed with hy -c.
• Fixed a bug in the compilation of multiple require s.
• Fixed various bugs in command-line option parsing.

0.18.0

Removals

• Python 2 is no longer supported.
• Support for attribute lists in defclass has been removed. Use setv and defn instead.
• Literal keywords are no longer parsed differently in calls to functions with certain names.
• hy.contrib.multi has been removed. Use cond or the PyPI package multipledispatch instead.

Other Breaking Changes

• HySequence is now a subclass of tuple instead of list. Thus, a HyList will never be equal to a list, and you can't use .append, .pop, etc. on a HyExpression or HyList.

New Features

• Added special forms py to pys that allow Hy programs to include inline Python code.
• Added a special form cmp for chained comparisons.
• All augmented assignment operators (except %= and ^=) now allow more than two arguments.
• Added support for function annotations (PEP 3107) and variable annotations (PEP 526).
• Added a function parse-args as a wrapper for Python's argparse.

Bug Fixes

• Statements in the second argument of assert are now executed.
• Fixed a bug that caused the condition of a while to be compiled twice.
• in and not-in now allow more than two arguments, as in Python.
• hy2py can now handle format strings.
• Fixed crashes from inaccessible history files.
• Removed an accidental import from the internal Python module test.
• Fixed a swarm of bugs in hy.extra.anaphoric.

Misc. Improvements

• Replaced the dependency clint with colorama.

0.17.0

Warning: Hy 0.17.x will be the last Hy versions to support Python 2, and we expect 0.17.0 to be the only release in this line. By the time 0.18.0 is released (in 2020, after CPython 2 has ceased being developed), Hy will only support Python 3.

Removals

• Python 3.4 is no longer supported.

New Features

• Python 3.8 is now supported.
• Format strings with embedded Hy code (e.g., f"The sum is {(+ x y)}") are now supported, even on Pythons earlier than 3.6.
• Added a special form setx to create Python 3.8 assignment expressions.
• Added new core functions list? and tuple.
• Gensyms now have a simpler format that's more concise when mangled (e.g., _hyx_XsemicolonXfooXvertical_lineX1235 is now _hyx_fooXUffffX1).

Bug Fixes

• Fixed a crash caused by errors creating temporary files during bytecode compilation.

0.16.0

Removals

• Empty expressions (()) are no longer legal at the top level.

New Features

• eval / hy_eval and hy_compile now accept an optional compiler argument that enables the use of an existing HyASTCompiler instance.
• Keyword objects (not just literal keywords) can be called, as shorthand for (get obj :key), and they accept a default value as a second argument.
• Minimal macro expansion namespacing has been implemented. As a result, external macros no longer have to require their own macro dependencies.
• Macros and tags now reside in module-level __macros__ and __tags__ attributes.

Bug Fixes

• Cleaned up syntax and compiler errors.
• You can now call defmain with an empty lambda list.
• require now compiles to Python AST.
• Fixed circular require\s.
• Fixed module reloading.
• Fixed circular imports.
• Fixed errors from from __future__ import ... statements and missing Hy module docstrings caused by automatic importing of Hy builtins.
• Fixed __main__ file execution.
• Fixed bugs in the handling of unpacking forms in method calls and attribute access.
• Fixed crashes on Windows when calling hy-repr on date and time objects.
• Fixed a crash in mangle for some pathological inputs.
• Fixed incorrect mangling of some characters at low code points.
• Fixed a crash on certain versions of Python 2 due to changes in the standard module tokenize.

0.15.0

Removals

• Dotted lists, HyCons, cons, cons?, and list* have been removed. These were redundant with Python's built-in data structures and Hy's most common model types (HyExpression, HyList, etc.).
• &key is no longer special in lambda lists. Use &optional instead.
• Lambda lists can no longer unpack tuples.
• ap-pipe and ap-compose have been removed. Use threading macros and comp instead.
• for/a has been removed. Use (for [:async ...] ...) instead.
• (except) is no longer allowed. Use (except []) instead.
• (import [foo]) is no longer allowed. Use (import foo) instead.

Other Breaking Changes

• HyExpression, HyDict, and HySet no longer inherit from HyList. This means you can no longer use alternative punctuation in place of square brackets in special forms (e.g. (fn (x) ...) instead of the standard (fn [x] ...)).

• Mangling rules have been overhauled; now, mangled names are always legal Python identifiers.

• _ and - are now equivalent, even as single-character names.

  • The REPL history variable _ is now *1.

• Non-shadow unary =, is, <, etc. now evaluate their argument instead of ignoring it.

• list-comp, set-comp, dict-comp, and genexpr have been replaced by lfor, sfor, dfor, and gfor, respectively, which use a new syntax and have additional features. All Python comprehensions can now be written in Hy.

• &-parameters in lambda lists must now appear in the same order that Python expects.

• Literal keywords now evaluate to themselves, and HyKeyword no longer inherits from a Python string type

• HySymbol no longer inherits from HyString.

New Features

• Python 3.7 is now supported.
• while and for are allowed to have empty bodies.
• for supports the various new clause types offered by lfor.
• defclass in Python 3 supports specifying metaclasses and other keyword arguments.
• Added mangle and unmangle as core functions.
• Added more REPL history variables: *2 and *3.
• Added a REPL variable holding the last exception: *e.
• Added a command-line option -E per CPython.
• Added a new module hy.model_patterns.

Bug Fixes

• hy2py should now output legal Python code equivalent to the input Hy code in all cases.
• Fixed (return) so it can exit a Python 2 generator.
• Fixed a case where -> and ->> duplicated an argument.
• Fixed bugs that caused defclass to drop statements or crash.
• Fixed a REPL crash caused by illegal backslash escapes.
• NaN can no longer create an infinite loop during macro-expansion.
• Fixed a bug that caused try to drop expressions.
• The compiler now properly recognizes unquote-splice.
• Trying to import a dotted name is now a syntax error, as in Python.
• defmacro! now allows optional arguments.
• Fixed handling of variables that are bound multiple times in a single let.

Misc. Improvements

• hy-repr uses registered functions instead of methods.
• hy-repr supports more standard types.

0.14.0

Removals

• Python 3.3 is no longer supported
• def is gone; use setv instead
• apply is gone; use the new #* and #** syntax instead
• yield-from is no longer supported under Python 2
• Periods are no longer allowed in keywords
• Numeric literals can no longer begin with a comma or underscore
• Literal Inf\s and NaN\s must now be capitalized like that

Other Breaking Changes

• Single-character "sharp macros" are now "tag macros", which can have longer names
• xi from hy.extra.anaphoric is now a tag macro #%
• eval is now a function instead of a special form

New Features

• The compiler now automatically promotes values to Hy model objects as necessary, so you can write (eval `(+ 1 ~n)) instead of (eval `(+ 1 ~(HyInteger n)))
• return has been implemented as a special form
• Added a form of string literal called "bracket strings" delimited by #[FOO[ and ]FOO], where FOO is customizable
• Added support for PEP 492 (async and await) with fn/a, defn/a, with/a, and for/a
• Added Python-style unpacking operators #* and #** (e.g., (f #* args #** kwargs))
• Added a macro comment
• Added EDN #_ syntax to discard the next term
• while loops may now contain an else clause, like for loops
• #% works on any expression and has a new &kwargs parameter %**
• Added a macro doc and a tag macro #doc
• get is available as a function
• ~@ (unquote-splice) form now accepts any false value as empty

Bug Fixes

• Relative imports (PEP 328) are now allowed
• Numeric literals are no longer parsed as symbols when followed by a dot and a symbol
• Hy now respects the environment variable PYTHONDONTWRITEBYTECODE
• String literals should no longer be interpreted as special forms or macros
• Tag macros (née sharp macros) whose names begin with ! are no longer mistaken for shebang lines
• Fixed a bug where REPL history wasn't saved if you quit the REPL with (quit) or (exit)
• exec now works under Python 2
• No TypeError from multi-arity defn returning values evaluating to None
• try forms are now possible in defmacro and deftag
• Multiple expressions are now allowed in try
• Fixed a crash when macroexpand\ing a macro with a named import
• Fixed a crash when with suppresses an exception. with now returns None in this case.
• Fixed a crash when --repl-output-fn raises an exception
• Fixed a crash when HyTypeError was raised with objects that had no source position
• assoc now evaluates its arguments only once each
• Multiple expressions are now allowed in the else clause of a for loop
• else clauses in for and while are recognized more reliably
• Statements in the condition of a while loop are repeated properly
• Argument destructuring no longer interferes with function docstrings
• Nullary yield-from is now a syntax error
• break and continue now raise an error when given arguments instead of silently ignoring them

Misc. Improvements

• read, read_str, and eval are exposed and documented as top-level functions in the hy module
• An experimental let macro has been added to hy.contrib.walk

0.13.1

Changed setup.py to require astor 0.5, since 0.6 isn't backwards-compatible.

0.13.0

Language Changes

• Pythons 2.6, 3.0, 3.1, and 3.2 are no longer supported
• let has been removed. Python's scoping rules do not make a proper implementation of it possible. Use setv instead.
• lambda has been removed, but fn now does exactly what lambda did
• defreader has been renamed to defsharp; what were previously called "reader macros", which were never true reader macros, are now called "sharp macros"
• try now enforces the usual Python order for its elements (else must follow all excepts, and finally must come last). This is only a syntactic change; the elements were already run in Python order even when defined out of order.
• try now requires an except or finally clause, as in Python
• Importing or executing a Hy file automatically byte-compiles it, or loads a byte-compiled version if it exists and is up to date. This brings big speed boosts, even for one-liners, because Hy no longer needs to recompile its standard library for every startup.
• Added bytestring literals, which create bytes objects under Python 3 and str objects under Python 2
• Commas and underscores are allowed in numeric literals
• Many more operators (e.g., **, //, not, in) can be used as first-class functions
• The semantics of binary operators when applied to fewer or more than two arguments have been made more logical
• (** a b c d) is now equivalent to (** a (** b (** c d))), not (** (** (** a b) c) d)
• setv always returns None
• When a try form executes an else clause, the return value for the try form is taken from else instead of the try body. For example, (try 1 (except [ValueError] 2) (else 3)) returns 3.
• xor: If exactly one argument is true, return it
• hy.core.reserved is now hy.extra.reserved
• cond now supports single argument branches

Bug Fixes

• All shadowed operators have the same arities as real operators
• Shadowed comparison operators now use and instead of & for chained comparisons
• partition no longer prematurely exhausts input iterators
• read and read-str no longer raise an error when the input parses to a false value (e.g., the empty string)
• A yield inside of a with statement will properly suppress implicit returns
• setv no longer unnecessarily tries to get attributes
• loop no longer replaces string literals equal to "recur"
• The REPL now prints the correct value of do and try forms
• Fixed a crash when tokenizing a single quote followed by whitespace

Misc. Improvements

• New contrib module hy-repr
• Added a command-line option --repl-output-fn