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Re: Simple argument question

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> "Bint" <bint@ign.com> wrote in message news:CB114269.B5F7%bint@ign.com...
>> Hi can someone answer a simple question involving arguments to functions?
>> 
>> I need to call a library function which expects an argument like this
>> Function(double pointlist[][3]);
>> 
>> My question is how do I make one of those if I am just wanting to malloc
>> the
>> memory?  Can I use a double pointer?
>> 
>> Can I have something like this:
>> double *points = (double *)malloc(10*3*sizeof(double));
>> 
>> for int (j = 0; j < 10; j++) {
>>     *(points + j*3 + 0) = x;
>>     *(points + j*3 + 1) = y;
>>     *(points + j*3 + 2) = z;
>> }
>> 
>> And then call the function with points as the argument?  It doesn't
>> compile
>> but I was wondering if I could cast it?  Or do I need something else
>> instead
>> of a double pointer for my points?
>> 
>> Does that make sense? I am confused about how to call the function with
>> anything but something like:
>> double array[500][3];
>> 
>> I don't want that because I don't know the number of points, see?
>> 
> Hi.
> When you create 2d arrays using new you may use pointer to pointer types ,
> but this is a different type from the built in array type.
> In your function argument your 2d array will decay into a pointer of type:
> double (*)[3]
> 
> Each dimensional array is pointed to by a pointer of type one dimension
> less. For example a one dimensional array of doubles is pointed to by a
> double*( the same as a pointer to a single double ). A 2-d array is pointed
> to by a type T(*)[S] . a 3d array is pointed to by a type T(*)[S1][S2] etc
> etc.
> 
> When you create your pointer with malloc you  are creating a pointer of type
> double* which is a pointer to a 1d array, or a pointer to a single double.
> But the function argument needs you to pass a 2d array.
> 

So how would I create and pass something valid to this function, say for an
array of [10][3], but specifying that 10 at run-time?  Do I use new instead
of malloc?

Thanks
B

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Simple argument question Bint <bint@ign.com> - 2011-12-16 18:46 -0600
  Re: Simple argument question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2011-12-17 01:13 +0000
    Re: Simple argument question Bint <bint@ign.com> - 2011-12-17 12:06 -0600
      Re: Simple argument question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2011-12-17 18:45 +0000
        Re: Simple argument question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2011-12-17 23:16 +0000
          Re: Simple argument question jt@toerring.de (Jens Thoms Toerring) - 2011-12-18 22:07 +0000
            Re: Simple argument question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2011-12-18 22:34 +0000
  Re: Simple argument question 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-17 00:13 -0800
    Re: Simple argument question Juha Nieminen <nospam@thanks.invalid> - 2011-12-17 08:16 +0000
      Re: Simple argument question 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-17 00:51 -0800
        Re: Simple argument question Juha Nieminen <nospam@thanks.invalid> - 2011-12-17 10:23 +0000
  Re: Simple argument question Goran <goran.pusic@gmail.com> - 2011-12-17 23:08 -0800
    Re: Simple argument question Heck <heckja_in@ordertostymieharvestersverizon.net> - 2012-01-05 09:59 -0500
  Re: Simple argument question Krice <paulkp@mbnet.fi> - 2011-12-18 00:46 -0800
    Re: Simple argument question jt@toerring.de (Jens Thoms Toerring) - 2011-12-18 22:14 +0000
      Re: Simple argument question Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-12-19 12:01 +0000
        Re: Simple argument question Tobias Müller <troplin@bluewin.ch> - 2011-12-19 17:17 +0000
          Re: Simple argument question Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-12-20 00:33 +0000
  Re: Simple argument question Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-12-18 17:03 +0000
    Re: Simple argument question 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-18 10:04 -0800

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