Python 3 supports keyword-only arguments as described in the immortal
PEP 3102. This commit implements keyword-only argument support for Hy
using a `&kwonly` lambda-list-keyword with semantics analogous how
`&optional` arguments are handled: `&kwonly` arguments are either a
symbol, in which case the keyword argument so named is mandatory, or a
two-element list, the first of which is the symbolic name of the keyword
argument and the second of which is its default value if not
supplied. If Hy is running under Python 2, attempting to use `&kwonly`
args will raise a HyTypeError.
This effort is with the aim of resolving #453.
Python 3.5's PEP 448 ("Additional Unpacking Generalizations") allows the
iterable- and dictionary- unpacking operators to be used more than once;
the implementation (see https://hg.python.org/cpython/rev/a65f685ba8c0)
gets rid of the optional `starargs` and `kwargs` arguments to `ast.Call`
and `ast.ClassDef`, instead using `ast.Starred` and `ast.keyword`
objects inside of the normal `args` and `keywords` lists,
respectively. This commit allows Hy's `apply` to work correctly with
this revised AST when running under Python 3.5.
As reported in issue #748, there was a bug in which passing a lambda
as the value of a :keyword argument would fail—
$ hy --spy
hy 0.10.1 using CPython(default) 3.4.0 on Linux
=> (sorted (range 10) :key (fn [x] (- x)))
from hy.core.language import range
sorted(range(10), key=_hy_anon_fn_1)
Traceback (most recent call last):
File "<input>", line 1, in <module>
NameError: name '_hy_anon_fn_1' is not defined
The function call would appear in the generated AST without being
preceded by the appropriate function definition corresponding to the
anonymous function argument value in the Hy source, causing either a
NameError (as in the example above), or erroneous reuse of whatever
function was already pointed to by the `_hy_anon_fn_` name referenced
in the list of keywords passed to `ast.Call`.
This commit aims to fix the problem by handling it in same way that
the expression/statement gap is bridged many other places in the
compiler, by adding the compiled value of the keyword argument to the
Result object being built during `_compile_collect`, with the
understanding that any Python statements implied by the argument value
will be appropriately preserved therein.
Python 3.5 will have a new commercial-at infix operator with the magic
methods __matmul__, __rmatmul__, and __imatmul__, unused as yet in the
standard library, but intended to represent matrix multiplication in
numerical code; see PEP 465 (https://www.python.org/dev/peps/pep-0465/)
for details. This commit (developed against Python 3.5 alpha 3) brings
support for this operator to Hy when running under Python 3.5 (or,
hypothetically as yet, greater). For Hy under Python <= 3.4, attempting
to use `@` in function-call position currently results in a NameError;
this commit does not change that behavior.
This is intended to resolve#668.
jcrocholl/pep8 (used by flake8, used in Hy's continuous integration
builds) introduced an imports-at-top-of-file check in 1.6.0 and a
line-breaks-around-binary-operators check in 1.6.2. This commit makes
nonfunctional changes to bring the Hy codebase in compliance with this
tool, fixing #764.
This code is heavily, *heavily* based off of Guillermo Vaya
(willyfrog)'s work... instead of defining its own keyword arg though, it
uses the "standard" :kwarg type, which is the main difference from
willyfrog's original branch.
Included tests and some documentation in the tutorial.
Also documented "apply" separately as an example of reproducing
*args and **kwargs.
When (fn) or (defn) does not get an arglist as first/second parameter,
emit a more descriptive error message, rather than an ugly traceback.
Fixes#716.
Reported-by: Joakim Tall
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Python has the keyword.iskeyword method we can leverage for Python
keywords, but we also need to address Hy builtins like 'get' or
'slice'.
And to make behavior compatible with Python 2 or 3, we also make
a special case to prevent assignment to False, True or None as
well as the Hy versions: false, true, null, and nil.
For non-Hy modules, we also check to make sure the symbol is not
part of the compiler. This allows shadow.hy to override "+" but
prevents general use from re-defn-ing 'get' or 'do'.
As noted in #600, Python 3 allows a return inside a generator
method, that raises a StopIteration and passes the return value
inside the 'value' attr of the exception.
To allow this behaviour we simple set 'contains_yield' while compiling
'yield', thus allowing a return statement, but only for Python 3. Then
when compiling the try-except, we check for contains_yield to decide
whether there will be a return.
This allows code like:
(defn gen []
(yield 3)
"goodbye")
to compile in both Py2 and Py3. The return value is simply ignored in
Python 2.
hy2py in Python 2 gives:
def g():
yield 3L
u'goodbye'
while hy2py in Python 3 gives:
def g():
yield 3
return 'goodbye'
Turns out return in yield started in Python 3.3
Also small DRYing in try handling.
Previously, writing a bare (try (foo)) would invoke Pokemon
exception catching (gotta catch 'em all) instead of the correct
behavior, which is to raise the exception if no handler is provided.
Note that this is a cute feature of Hy, as a `try` with no `except`
is a syntax error. We avoid the syntax error here because we don't
use Python's compiler, which is the only thing that can throw
Syntax Errors. :D
Fixes#555.
The yield-from that existed previously wasn't actually implementing the
full complexity of "yield from":
http://legacy.python.org/dev/peps/pep-0380/#formal-semantics
... this includes passing along errors, and many other things.
Also removes the yield-from backport macro, since it does not seem
possible at present to conditionally build macros.
Thus, there is no longer yield-from on pre-python-3.3 systems.
Includes updated docs and tests to reflect all this.
When (import) encounters anything but a HySymbol or HyList, raise an
exception, as that is not valid in Hy. Previously, anything other than a
HySymbol or HyList was simply ignored, turning that particular import
into a no-op, which was both wrong and confusing.
Reported-by: Richard Parsons <richard.lee.parsons@gmail.com>
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
This version is much simpler.
At the point that the exception is raised, we don't have access to
the actual source, just the current expression. but as the
exception percolates up, we can intercept it, add the source and
the re-raise it.
Then at the final point, in the cmdline handler, we can choose to
let the entire traceback print, or just the simpler, direct error
message.
And even with the full traceback, the last bit is nicely formatted
just like the shorter, simpler message.
The error message is colored if clint is installed, but to avoid
yet another dependency, you get monochrome without clint.
I'm sure there is a better way to do the markup, the current method
is kludgy but works.
I wish there was more shared code between HyTypeError and LexException
but they are kind of different in some fundamental ways.
This doesn't work (yet) with runtime errors generated from Python,
like NameError, but I have a method that can catch NameError and turn it
into a more pleasing output.
Finally, there is no obvious way to raise HyTypeError from pure Hy code,
so methods in core/language.hy throw ugly TypeError/ValueError.
