Re: issorted & sortrows

[John W. Eaton]

On 11-Feb-2009, Jaroslav Hajek wrote:

| On Wed, Feb 11, 2009 at 4:02 PM, John W. Eaton <address@hidden> wrote:
|
| > +bool (*_sortrows_comparator (sortmode mode,
| > +                             const Array<Complex>& a , bool allow_chk))
| > +(Complex, Complex)
| > +{
| >
| > This has me scratching my head.  Maybe a typedef would help here, so
| > you could write this as
| >
| >  sortrows_comparator_function
| >  xsortrows_comparator (const Complex&, const Complex&)
| >  {
| >
| 
| Here, I simply copied the template from Array.cc
| 
| template<class T>
| bool (*_sortrows_comparator (...))(T, T) { ... }
| 
| I don't think this syntax can be simplified without introducing a
| traits class. For the specializations, one can introduce explicit
| typedefs (like you have shown) but it seems to me that it obscures
| somewhat the fact that it's a specialization (matching signatures).

I don't see why a traits class is needed.  Won't something like the
following work?

  diff --git a/liboctave/Array-d.cc b/liboctave/Array-d.cc
  --- a/liboctave/Array-d.cc
  +++ b/liboctave/Array-d.cc
  @@ -52,11 +52,10 @@
     return lo_ieee_isnan (x) ? ! lo_ieee_isnan (y) : x > y;
   }

  -bool (*_sortrows_comparator (sortmode mode, 
  -                             const Array<double>& a , bool allow_chk)) 
  -(double, double)
  +octave_sort<double>::compare_fcn_type
  +_sortrows_comparator (sortmode mode, const Array<double>& a , bool allow_chk)
   {
  -  bool (*result) (double, double) = 0;
  +  octave_sort<double>::compare_fcn_type result = 0;

     if (allow_chk)
       {
  diff --git a/liboctave/oct-sort.h b/liboctave/oct-sort.h
  --- a/liboctave/oct-sort.h
  +++ b/liboctave/oct-sort.h
  @@ -135,6 +135,8 @@

     static bool ascending_compare (T, T);
     static bool descending_compare (T, T);
  +
  +  typedef bool (*compare_fcn_type) (T, T);

   private:


It seems much clearer to have a typedef like this and be able to write
the function as

  octave_sort<double>::compare_fcn_type
  _sortrows_comparator (sortmode mode, const Array<double>& a , bool allow_chk)
  {
    octave_sort<double>::compare_fcn_type result = 0;
    ...

instead of 

  bool (*_sortrows_comparator (sortmode mode, 
                              const Array<double>& a , bool allow_chk)) 
  (double, double)
  {
    bool (*result) (double, double) = 0;
    ...

I now see I had it wrong in my earlier message because I was having
trouble deciphering the declaration.

If you don't like mixing the octave_sort and Array classes for this,
then I think you can put the typedef in the Array class instead.

BTW, why isn't _sortrows_comparator a member of the Array class?

jwe