validate string is valid maths

[Remco Gerlich]

Hi,

It seems that for every group of 2 or more +-/* signs, one of the following
holds:

- The group starts with '-', everything after it should be dropped,
otherwise
- The second character is '-', everything after it should be dropped,
otherwise
- Drop everything after the first.

That should turn into one short regex. Did I miss something?

Remco

On Jan 28, 2008 4:10 PM, <Matthew_WARREN at bnpparibas.com> wrote:

> Hi pythoners.
>
> I am generating strings of length n, randomly from the symbols
>
> +-/*0123456789
>
> What would be the 'sensible' way of transforming the string, for example
> changing '3++++++8' into 3+8
> or '3++--*-9' into '3+-9' such that  eval(string) will always return a
> number?
>
> in cases where multiple symbols conflict in meaning (as '3++--*-9' the
> earliest valid symbols in the sequence should be preserved
>
> so for example,
>
> '3++*/-9'         =     3+-9
> '45--/**/+7'      =     45-+7
> '55/-**+-6**'     =     55/-6
>
> ...that is, unless there is a canonical method for doing this that does
> something else instead..
>
>
> this sounds like homework. It's not. I like making problems up and it's a
> slow work day. So, as an aside, there is no real reason I want to do this,
> nor other problem to solve, nor other background to what I'm trying to
> achieve ;) other than twiddling with python.
>
> Matt.
>
>
>
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