How to replace first substring if regexprep doesn't work

Hi!

I have some task in which I need sometimes to replace the first substring with another. In this task, I can get inside the string specific symbols, like for example plus (+). Here is my usecase:

 stack='X+S+X+S';
 left_side='X+S';
 right_side='S';

Now I need to replace the first 'X+S' with 'S'. strrep doesn't work for me, because I get

 stack=strrep(stack, left_side, right_side);
 stack='S+S';

So I used regexprep, but that doesn't work either, in fact it does nothing

 stack=regexprep(stack, left_side, right_side, 'once');
 stack='X+S+X+S';

I guess it's because plus symbol has some meaning in regexp. So is there any solution for me? Solution that will replace only the first substring with the possibility of any symbols in it?

Thanks for anything!

Answer 1

[Walter Roberson]

+ is special to regexp. USe http://www.mathworks.com/help/matlab/ref/regexptranslate.html

Answer 2

[Azzi Abdelmalek]

stack='X+S+X+S'
left_side='X+S'
right_side='S'
regexprep(stack, 'X+++S', 'S',1)