A dialect of Lisp that's embedded in Python
parse-args is no longer implemented with eval; so e.g. you should now say :type int instead of :type 'int.hy -c.require s.defclass has been removed. Use setv and defn instead.hy.contrib.multi has been removed. Use cond or the PyPI package multipledispatch instead.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.py to pys that allow Hy programs to include inline Python code.cmp for chained comparisons.%= and ^=) now allow more than two arguments.parse-args as a wrapper for Python's argparse.assert are now executed.while to be compiled twice.in and not-in now allow more than two arguments, as in Python.hy2py can now handle format strings.test.hy.extra.anaphoric.clint with colorama.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.
f"The sum is {(+ x y)}") are now supported, even on Pythons earlier than 3.6.setx to create Python 3.8 assignment expressions.list? and tuple._hyx_XsemicolonXfooXvertical_lineX1235 is now _hyx_fooXUffffX1).()) are no longer legal at the top level.eval / hy_eval and hy_compile now accept an optional compiler argument that enables the use of an existing HyASTCompiler instance.(get obj :key), and they accept a default value as a second argument.require their own macro dependencies.__macros__ and __tags__ attributes.defmain with an empty lambda list.require now compiles to Python AST.require\s.from __future__ import ... statements and missing Hy module docstrings caused by automatic importing of Hy builtins.__main__ file execution.hy-repr on date and time objects.mangle for some pathological inputs.tokenize.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.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.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.
_ 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.
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.mangle and unmangle as core functions.*2 and *3.*e.-E per CPython.hy.model_patterns.hy2py should now output legal Python code equivalent to the input Hy code in all cases.(return) so it can exit a Python 2 generator.-> and ->> duplicated an argument.defclass to drop statements or crash.NaN can no longer create an infinite loop during macro-expansion.try to drop expressions.unquote-splice.defmacro! now allows optional arguments.let.hy-repr uses registered functions instead of methods.hy-repr supports more standard types.def is gone; use setv insteadapply is gone; use the new #* and #** syntax insteadyield-from is no longer supported under Python 2Inf\s and NaN\s must now be capitalized like thatxi from hy.extra.anaphoric is now a tag macro #%
eval is now a function instead of a special form(eval `(+ 1 ~n)) instead of (eval `(+ 1 ~(HyInteger n)))
return has been implemented as a special form#[FOO[ and ]FOO], where FOO is customizableasync and await) with fn/a, defn/a, with/a, and for/a
#* and #** (e.g., (f #* args #** kwargs))comment
#_ syntax to discard the next termwhile loops may now contain an else clause, like for loops#% works on any expression and has a new &kwargs parameter %**
doc and a tag macro #doc
get is available as a function~@ (unquote-splice) form now accepts any false value as emptyPYTHONDONTWRITEBYTECODE
! are no longer mistaken for shebang lines(quit) or (exit)
exec now works under Python 2defn returning values evaluating to None
try forms are now possible in defmacro and deftag
try
macroexpand\ing a macro with a named importwith suppresses an exception. with now returns None in this case.--repl-output-fn raises an exceptionHyTypeError was raised with objects that had no source positionassoc now evaluates its arguments only once eachelse clause of a for loopelse clauses in for and while are recognized more reliablywhile loop are repeated properlyyield-from is now a syntax errorbreak and continue now raise an error when given arguments instead of silently ignoring themread, read_str, and eval are exposed and documented as top-level functions in the hy modulelet macro has been added to hy.contrib.walk
Changed setup.py to require astor 0.5, since 0.6 isn't backwards-compatible.
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 diddefreader 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 Pythonbytes objects under Python 3 and str objects under Python 2**, //, not, in) can be used as first-class functions(** a b c d) is now equivalent to (** a (** b (** c d))), not (** (** (** a b) c) d)
setv always returns None
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 ithy.core.reserved is now hy.extra.reserved
cond now supports single argument branchesand instead of & for chained comparisonspartition no longer prematurely exhausts input iteratorsread and read-str no longer raise an error when the input parses to a false value (e.g., the empty string)yield inside of a with statement will properly suppress implicit returnssetv no longer unnecessarily tries to get attributesloop no longer replaces string literals equal to "recur"do and try formshy-repr
--repl-output-fn
This release brings some quite significant changes on the language and as a result very large portions of previously written Hy programs will require changes. At the same time, documentation and error messages were improved, hopefully making the language easier to use.
let, with and defclass
&kwonly, &kwargs and &key arguments#{1 2 3})setv, del and cond
=, !=, <, >, <=, >=)partition form for chunking collection to n-sized tuplesdefn-alias and demacro-alias moved into hy.contrib.alias
None is returned instead of the last form in --init--
for and cond can take a multi-expression bodyapply now mangles strings and keywords according to Hy mangling rulesif
defreader can use strings as macro namesas-> macro addedrequire syntax changed and now supports same features as import
defmulti changed to work with dispatching functiondefmulti renamed to defn
contrib
defmacro! added for once-only evaluation for parameterscomp, constantly, complement and juxt addedfor doesn't have bodydefclass can have properties / methods with built-in nameshy2py and hyc
&rest can be used after &optional
(eval ...)
contrib.walk: Coerce non-list iterables into list formcase and switch)ap-pipe and ap-compose macros#@ reader macro for with-decoratoreval parametersand and or short-circuitand and or accept zero or more argumentsread-str for tokenizing a linebotsbuildbots moved to contribxi forms (anonymous function literals)if form optimizations in some casesxor operatorap-if requires then branchinc, dec, odd?, even?, etc.) aren't type checkedimport_file_to_globals added for use in emacs inferior lisp modehy.core.reserved added for querying reserved wordshy2py can use standard input instead of a filealias, curry, flow and meth removed from contrib
contrib.anaphoric moved to hy.extra