Aw: Re: regexp: matching expressions b4 and after ....

[giovanni . lombardo]

Hi,

thanks for the reply Ben. 
As you see in your attempt, also the first "(-1)" gets replaced, which is 
exactly what the regexprep example command (in MATLAB) avoids.

In practice I'm looking for the look-around operators for OCTAVE as described 
in MATLAB.


 
----- Original Nachricht ----
Von:     Ben Abbott <address@hidden>
An:      address@hidden
Datum:   08.09.2008 18:22
Betreff: Re: regexp: matching expressions b4 and after ....

> On Monday, September 08, 2008, at 11:38AM, <address@hidden>
> wrote:
> >Hi,
> >
> >I'm trying to convert a set of matlab codes into Octave. These codes
> heavily use string manipulation functions
> >
> >In particular I'm trying to extract a set of equations from an ASCII file.
> From these equations I extract/replace variables etc.
> >
> >So, for example, I have g="x^(-1)+y(-1)+z(-1)=0"
> >
> >I need to extract/replace x, y and (-1). So, for example, I used the
> command regexprep(g,'(?<=[a-z]*)\(\-[1-9]*\)','\_minus1')
> >
> >which returned "x^(-1)+y_minus1+z_minus1"
> >
> >Can I do the same in Octave? How?
> >
> 
> Doesn't work for me either
> 
> octave:1> g="x^(-1)+y(-1)+z(-1)=0"
> g = x^(-1)+y(-1)+z(-1)=0
> octave:2> 
> octave:2> regexprep(g,'(?<=[a-z]*)\(\-[1-9]*\)','\_minus1') 
> error: syntax error in pattern
> 
> Running Matlab2007b
> 
> >> g='x^(-1)+y(-1)+z(-1)=0';
> >> regexprep(g,'(?<=[a-z]*)\(\-[1-9]*\)','\_minus1')
> ans =
> x^_minus1+y_minus1+z_minus1=0
> 
> I'd suggest you try to isolate the error. Perhaps if the developers knew
> where the specific problem was they could fix it.
> 
> I'm not experienced with regexp, but the simpler one below works for your
> example.
> 
> regexprep(g,'\(\-[1-9]*\)','_minus1') 
> ans = x^_minus1+y_minus1+z_minus1=0
> 
> Ben
>