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.
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
As a result:
* functions such as `nth` should work correctly on iterators;
* `nth` will raise `IndexError` (in a fashion consistent with `get`)
when the index is out of bounds;
* `take`, etc. will raise `ValueError` instead of returning
an ambiguous value if the index is negative;
* `map`, `zip`, `range`, `input`, `filter` work the same way (Py3k one)
on both Python 2 and 3 (see #523 and #331).
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.
