[Python-ideas] Macros for Python

[Andrew Barnert]

On Apr 24, 2013, at 8:05, Haoyi Li <haoyi.sg at gmail.com> wrote:
> You actually can get a syntax like that without macros, using stack-introspection, locals-trickery and lots of `eval`. The question is whether you consider macros more "extreme" than stack-introspection, locals-trickery and `eval`! A JIT compiler will probably be much happier with macros.

That last point makes this approach seem particularly interesting to me, which makes me wonder: Is your code CPython specific, or does it also work with PyPy (or Jython or Iron)? While PyPy is obviously a whole lot easier to mess with in the first place than CPython, having macros at the same language level as your code is just as interesting in both implementations.

> 
> On Wed, Apr 24, 2013 at 10:35 AM, Terry Jan Reedy <tjreedy at udel.edu> wrote:
>> On 4/23/2013 11:49 PM, Haoyi Li wrote:
>>> I thought this may be of interest to some people on this list, even if
>>> not strictly an "idea".
>>> 
>>> I'm working on MacroPy <https://github.com/lihaoyi/macropy>, a little
>>> 
>>> pure-python library that allows user-defined AST rewrites as part of the
>>> import process (using PEP 302).
>> 
>> From the readme
>> '''
>> String Interpolation
>> 
>> a, b = 1, 2
>> c = s%"%{a} apple and %{b} bananas"
>> print c
>> #1 apple and 2 bananas
>> '''
>> I am a little surprised that you would base a cutting edge extension on Py 2. Do you have it working with 3.3 also?
>> 
>> '''Unlike the normal string interpolation in Python, MacroPy's string interpolation allows the programmer to specify the variables to be interpolated inline inside the string.'''
>> 
>> Not true as I read that.
>> 
>> a, b = 1, 2
>> print("{a} apple and {b} bananas".format(**locals()))
>> print("%(a)s apple and %(b)s bananas" % locals())
>> #1 apple and 2 bananas
>> #1 apple and 2 bananas
>> 
>> I rather like the anon funcs with anon params. That only works when each param is only used once in the expression, but that restriction is the normal case.
>> 
>> I am interested to see what you do with pattern matching.
>> 
>> tjr
>> 
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