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Emacs Rocks

I had a boring text editing task. I'm using a text file that refers to components by a number and after writing it I realised that I need those component numbers to be incrementing.

I had:

Bus.con = [
101 138 1 0 2 1;
102 138 1 0 2 1;
...
124 138 1 0 2 1;
201 138 1 0 2 1;
202 138 1 0 2 1;
...
];

Shunt.con = [
106 100 138 60 0 -1 1;
206 100 138 60 0 -1 1;
306 100 138 60 0 -1 1;
];

I wanted:

Bus.con = [
1 138 1 0 2 1;
2 138 1 0 2 1;
...
24 138 1 0 2 1;
25 138 1 0 2 1;
26 138 1 0 2 1;
...
];

Shunt.con = [
6 100 138 60 0 -1 1;
30 100 138 60 0 -1 1;
54 100 138 60 0 -1 1;
];

One problem is that the component number might be the same as a parameter (which I don't want to change). Two tools here:

  1. re-builder - interactively build a regular expression. 
  2. (query)-replace-regexp - replace a regexp with another 
  3. elisp in regexps - do anything with a regexp
This led to the following three replacements:
replace " 1\([0-2][0-9]\) " with " \1 "
replace " 2\([0-2][0-9]\) " with " \,(+ 24 string-to-int \1)) "
replace " 3\([0-2][0-9]\) " with " \,(+ 48 string-to-int \1)) "
by doing it as a query I made sure I was only replacing the correct stuff. 

I even had time to write this blog post. 

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