0.12.0

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.

Language Changes

• New syntax for let, with and defclass
• defmacro will raise an error on &kwonly, &kwargs and &key arguments
• Keyword argument labels to functions are required to be strings
• slice replaced with cut to stop overloading the python built-in
• removed reduntant throw, catch, progn, defun, lisp-if, lisp-if-not,
  filterfalse, true, false and nil
• global now takes multiple arguments
• Nonlocal keyword (Python 3 only)
• Set literals (#{1 2 3})
• Keyword-only arguments (Python 3 only)
• Setv can assign multiple variables at once
• Empty form allowed for setv, del and cond
• One-argument division, rationals and comparison operators (=, !=, <, >, <=, >=)
• partition form for chunking collection to n-sized tuples
• defn-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 body
• Hex and octal support for integer literals
• apply now mangles strings and keywords according to Hy mangling rules
• Variadic if
• defreader can use strings as macro names
• as-> macro added
• require syntax changed and now supports same features as import
• defmulti changed to work with dispatching function
• old defmulti renamed to defn
• Lazy sequences added to contrib
• defmacro! added for once-only evaluation for parameters
• comp, constantly, complement and juxt added
• keyword arguments allowed in method calls before the object

Bug Fixes

• Better error when for doesn't have body
• Better error detection with list comprehensions in Python 2.7
• Setting value to callable will raise an error
• defclass can have properties / methods with built-in names
• Better error messages on invalid macro arguments
• Better error messages with hy2py and hyc
• Cmdline error to string conversion.
• In python 3.3+, generator functions always return a value
• &rest can be used after &optional

Misc. Improvements

• Version information includes SHA1 of current commit
• Improved Python 3.5 support
• Allow specification of global table and module name for (eval ...)
• General documentation improvements
• contrib.walk: Coerce non-list iterables into list form
• Flow macros (case and switch)
• ap-pipe and ap-compose macros
• #@ reader macro for with-decorator
• Type check eval parameters
• and and or short-circuit
• and and or accept zero or more arguments
• read-str for tokenizing a line
• botsbuildbots moved to contrib
• Trailing bangs on symbols are mangled
• xi forms (anonymous function literals)
• if form optimizations in some cases
• xor operator
• Overhauled macros to allow macros to ref the compiler
• ap-if requires then branch
• Parameters for numeric operations (inc, dec, odd?, even?, etc.) aren't type checked
• import_file_to_globals added for use in emacs inferior lisp mode
• hy.core.reserved added for querying reserved words
• hy2py can use standard input instead of a file
• alias, curry, flow and meth removed from contrib
• contrib.anaphoric moved to hy.extra