• Danny Arends (14/14) Feb 10 2013 I need to call some C code which takes a double**
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (29/43) Feb 10 2013 You need to use two properties of slices:
• Danny Arends (2/2) Feb 10 2013 Thanks so much !
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (13/15) Feb 10 2013 We all know the feeling. :)

"Danny Arends" <Danny.Arends gmail.com> writes:

I need to call some C code which takes a double**

In D I have a dynamic array X, Whats a good way of doing this ?

#SNIP

extern(C){
   void toCall(double** X, size_t d1, size_t d2);
}

void main(){
   double[][] X;

   // How to be able to:
   toCall(X, X.length, X[0].length);
}



Danny Arends
http://www.dannyarends.nl

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 02/10/2013 11:38 AM, Danny Arends wrote:
 I need to call some C code which takes a double**

 In D I have a dynamic array X, Whats a good way of doing this ?

 #SNIP

 extern(C){
 void toCall(double** X, size_t d1, size_t d2);
 }

 void main(){
 double[][] X;

 // How to be able to:
 toCall(X, X.length, X[0].length);
 }



 Danny Arends
 http://www.dannyarends.nl

You need to use two properties of slices:

.ptr: Pointer to the first element
.length: The number of elements

import std.stdio;
import std.algorithm;
import std.range;

extern(C)
{
     void toCall(double** X, size_t d1, size_t d2)
     {
         for (size_t row = 0; row != d1; ++row) {
             for (size_t column = 0; column != d2; ++column) {
                 writefln("%s,%s: %s", row, column, X[row][column]);
             }
         }
     }
}

void main(){
     double[][] X = [ [ 1, 2, 3 ], [ 10, 20, 30 ] ];

     double*[] X_c = X.map!(d => d.ptr).array;
     toCall(X_c.ptr, X_c.length, X[0].length);
}

The line with map is the equivalent of the following:

     double*[] X_c;
     foreach (slice; X) {
         X_c ~= slice.ptr;
     }

Ali

"Danny Arends" <Danny.Arends gmail.com> writes:

Thanks so much !

Why is this not easy 2 find :P

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 02/10/2013 12:05 PM, Danny Arends wrote:
 Thanks so much !

 Why is this not easy 2 find :P

We all know the feeling. :)

For future reference:

The spec:

   http://dlang.org/arrays.html#array-properties

TDPL:

   4.6 Arrays' Maverick Cousin: The Pointer

Programming in D:

   http://ddili.org/ders/d.en/pointers.html

   ("The .ptr property of arrays" section.)

Ali

-- 
D Programming Language Tutorial: http://ddili.org/ders/d.en/index.html