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

[Ben Abbott]

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