RE: [Vxl-users] VCL: Sorting with user-defined classes

[Ian S. <ian...@st...>]

try using references in your comparator (in your first case)

   bool operator<( const (peak*) &p2) const {
     return val < p2->val; }


> -----Original Message-----
> From: Andreas Turina [mailto:at...@vi...]
> Sent: Friday, February 01, 2002 3:17 PM
> To: vxl...@li...
> Subject: [Vxl-users] VCL: Sorting with user-defined classes
> 
> 
> Hi,
> 
> I have a user-defined datastructure where multiple instances 
> thereof are
> stored in a vcl_vector. This vector needs to be sorted.
> 
> More precisely, my simple datastructure looks like this:
> 
> struct peak
> {
>   peak(int xx, int yy, double vval):
>   x(xx), y(yy), val(vval) {};
>   int x;
>   int y;
> 
>   double val;       // Sort key
> 
>   bool operator<( const peak* p2) const {
>     return val < p2->val;
>   }
> };
> 
> and
> 
> vcl_vector<peak*> pl;
> 
> The sort key is val.
> 
> I experimented with two instantiation files in a Templates/ directory:
> VCL_VECTOR_INSTANTIATE(peak*);
> 
> VCL_SORT_INSTANTIATE(vcl_vector<peak*>::iterator, peak);
> 
> and tried the sort as follows:
> 
> vcl_sort( pl.begin(), pl.end() );
> 
> It seems to me that the entries in pl are sorted according to their
> address values in memory, rather than to the intended sort key val.
> 
> 1. Any suggestions how the vcl_vector<peak*> can be sorted 
> correctly (or
> what did I do wrong ) ?
> 
> 2. An alternative way is to make use of a function object, like
> 
> struct peak_comp{
>   bool operator()(const peak* a, const peak* b){
>     return a->val < b->val;
>   }
> };
> peak_comp pcomp;
> sort(pl.begin(), pl.end(), pcomp);
> 
> Any ideas how can this be done with the vxl version I currently
> use ?
> 
> targetjr-5.0b  (ok, this version is quite old..)
> gcc-2.95.2
> Solaris 5.6
> 
> Thanks !
> 
> Regards,
> 
>  Andreas
> 
> 
> 
> 
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