Re: Refactoring in Emacs

[Dmitry Antipov]

On 07/31/2012 10:06 PM, Eli Zaretskii wrote:

> > IIUC real refactoring of C should imply preprocessing and full
> > syntactic analysis
>
> Why is that?  Can you give a couple of examples?

It's easy to use regexps to make

foo (2, 1);

from

foo (1, 2);

But it may be very tricky or even impossible to do the same for:

1) foo (bar (x, y, z), baz (a, b, c));

2) foo (bar (x, y, foo (z, 1)), baz (foo (a, b) > 0 ? c : d, e, f));

3) foo (
#ifdef AAA
     a,
#else
     b,
#endif
     c > 0 ? c : -c);

etc.

For 2), syntax tree may looks like:

         ++++++++++++[foo]++++++++++++
         +                           +
    +++[bar]+++              ++++++[baz]++++++
    +    +    +              +       +       +
    x    y +[foo]+     ++++[> ?]++++ e       f
           +     +     +     +     +
           z     1  +[foo]+  c     d
                    +     +
                    a     b

So, refactoring is (hm, relatively) simple: you should traverse the tree,
look for

   +[foo]+
   +     +
   x     y

pattern and swap subtrees.

Check http://gcc-melt.org, it looks very similar to what I'm thinking about.

Dmitry