[pypy-dev] __builtin__ module

Armin Rigo arigo at tunes.org
Fri Jan 24 17:10:08 CET 2003

Hello Scott,

On Fri, Jan 24, 2003 at 07:43:13AM -0500, Scott Fenton wrote:
> I disagree. My feeling about this is probably that everything that can
> be expressed as a function should be in pure python, and that which 
> can't should probably be C

No!  I was not saying it should be in C.  *Nothing* should be in C.  I'm using 
the word "built-in" to mean a function at the interpreter-level, as opposed to 
a function at the application-level.

I still think that the complexity of "string modulo" is best written as a 
(non-built-in) Python function.

A thing like chr() on the other hand is trivial to implement as a built-in, 
with code like this:

  def builtin_chr(v):   # v is a PyInt class instance
      i = v.parse_long()
      if i not in range(256):
          raise EPython(PyExc(ValueError),
                        PyStr('chr() arg not in range(256)')
      return PyStr(chr(i))

Compare this with bltinmodule.c:chr().

Yes, I know there is still a call to 'chr()' in my implementation.  But I'm at
the interpreter level.  The above function (including its chr() call) is easy
to translate to C to make the equivalent of bltinmodule.c:chr().

BTW the syntax "i not in range(256)" is more conceptual than "i<0 or i>=256" 
and expresses better what we are testing for (as the error message suggests 
too).  The above code is a typical example of how I see "built-in" functions 
could be written.  The function is "built-in" not because it is written in 
another language but because it works at the interpreter level.

A bientôt,


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