Yet another attempt at a safe eval() call

Grant Edwards invalid at invalid.invalid
Fri Jan 4 19:43:46 CET 2013


On 2013-01-04, Chris Angelico <rosuav at gmail.com> wrote:
> On Sat, Jan 5, 2013 at 5:09 AM, Grant Edwards <invalid at invalid.invalid> wrote:
>> The error messages are still pretty cryptic, so improving
>> that will add a few more lines.  One nice thing about the ast code is
>> that it's simple to add code to allow C-like character constants such
>> that ('A' === 0x41).  Here's the first pass at ast-based code:
>
> Looks cool, and fairly neat! Now I wonder, is it possible to use that
> to create new operators, such as the letter d? Binary operator, takes
> two integers...

I don't think you can define new operators.  AFAICT, the
lexing/parsing is done using the built-in Python grammar. You can
control the behavior of the predefined operators and reject operators
you don't like, but you can't add new ones or change precedence/syntax
or anything like that.

If you want to tweak the grammar itself, then I think you need to use
something like pyparsing.

-- 
Grant Edwards               grant.b.edwards        Yow! I own seven-eighths of
                                  at               all the artists in downtown
                              gmail.com            Burbank!



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