Re: possible Improving diff algoritm

[Geert Bosch <bosch@adacore.com>]

On Dec 12, 2012, at 20:55, Morten Welinder <mwelinder@gmail.com> wrote:
> I was merely asking if an algorithm to pick between the
> 2+ choices was allowed to look at the contents of the
> lines.
> 
> I.e., an algorithm would look at the C comment
> example and determine that the choice starting containing
> a full inserted comment is preferable over the one that
> appears to close one comment and open a new.
> 
> And the in inserted-function case it would prefer the one
> where the matching { and } are in correct order.

        /**                         +    /**                         
   +     * Default parent           +     * Default parent           
   +     *                          +     *                          
   +     * @var int                 +     * @var int                 
   +     * @access protected        +     * @access protected        
   +     * @index                   +     * @index                   
   +     */                         +     */                         
   +    protected $defaultParent;   +    protected $defaultParent;   
   +                                +                                
   +    /**                              /**                         

It would seem that just looking at the line length (stripped) of
the last line, might be sufficient for cost function to minimize.
Here the some would be 3 vs 0. In case of ties, use the last
possibility with minimum cost.

I think it would be nice if the cost function we choose does not
depend on file type, as that is something that is very dependent
on the exact local configuration and might hinder comparison of
patches. If something really simple gets us 90% there, that would
be preferable over extra complexity.

  -Geert

Junio's other example:

   }

  +void new_function(void)
  +{
  +  printf("hello, world.\n");
  +}
  +
   void existing_one(void)
   {
     printf("goodbye, world.\n");

=> Cost 0

  +}
  +
  +void new_function(void)
  +{
  +  printf("hello, world.\n");
   }
=> Cost 27

Kevin's example:
    /**
+     * Default parent
+     *
+     * @var int
+     * @access protected
+     * @index
+     */
+    protected $defaultParent;
+
+    /**

=> Cost 3

+   /**
+     * Default parent
+     *
+     * @var int
+     * @access protected
+     * @index
+     */
+    protected $defaultParent;
+
     /**
=> cost 0