[pypy-dev] Internship and bug report

[Amaury Forgeot d'Arc]

2012/6/19 Leonard de HARO <leonard.de.haro at ens.fr>

> Hello,
>
> I'm a french undergraduated CS. student currently doing an internship in
> Santigo's University under the supervision of Eric Tanter. I'm working on
> the meta JIT compiler provided in the pypy project, trying to document
> it's performance on different kind of interpreters. I started two weeks
> ago.
>
> I have a problem with the translation toolchain. I've been writing an
> interpreter for a small language inspired by Shriram Krishnamurthi's F1WAE
> from his book "Programming Languages: Application and Interpretation".
> My problem is the following: I have an interpreter that seems to work
> perfecty (at least on my examples) when I use pypy interpreters, but
> whenever I translate it, execution fails. The fact is: I have identified
> the source of the problem but I don't understand it.
> If you look at the parser file, on line 184, there is a "print"
> instruction. With this instruction on comment, the translated version of
> RPinterpret executed on test10run10 gets a Stack Overflow. Use a
> translated version of the same file (RPinterpret.py) with the print
> instruction in parser.py, you get the normal behavior (which you have
> anyway using "pypy RPinterpret.py test10runs10").


> Looks like a bug, but since I'm a beginer (both on this work and on Python
> in general), maybe I have missed something.
>

Hum, looks like a RPython oddness.
It seems that you have to catch IndexError for IndexError to be raised by
the operation...

def CutWord(string, i):
    try:
        if string[i] in (' ', '\n', '\t'):
            return i
    except IndexError:
        return i
    return CutWord(string, i+1)

But I think a loop would be much more efficient...

-- 
Amaury Forgeot d'Arc
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