possible bug with the stl inner_product() function

[Graham M. Seed]

Dear Sir/Madam

The following program illustrates uses of the 
inner_product() function of the c++ STL. I'm using version 
2.91.66 gcc/g++ compiler running at Red Hat Linux 6.2.

The default operators for the inner_product() function are 
*,+ which gives a final answer of 70 as expected. However, 
when we specify the contrary case of +,* operators then I'd 
expect the result to be 5760 but it is still 70??

If this isn't a bug then it certainly doesn't agree with 
the mathematical interpretation of the inner product.

//...
void main ()
	{
   int array1[] = { 1, 2, 3, 4 };
   int array2[] = { 5, 6, 7, 8 };

   ostream_iterator<int> out (cout, " ") ;
   cout << "array1: " ;
   copy (array1, array1+4, out) ;
   cout << endl ;
   cout << "array2: " ;
   copy (array2, array2+4, out) ;
   cout << endl ;

   int ip1 = inner_product (array1, array1+4, array2, 0) ;
   cout << "ip1: " << ip1 << endl ; // O/P 70 as expected

   int ip2 = inner_product (array1, array1+4, array2, 0, plus<int>(), multiplies<int>()) ;
   cout << "ip2: " << ip2 << endl ; // O/P still 70 when 
should be 5760?
   }

Wishes

Graham
--
Dr. Graham M. Seed
Dept. of Mech. & Chem. Eng.
Heriot-Watt University
Riccarton, 
Edinburgh, EH14 4AS
Scotland, UK
T: +44(0)131 449 5111; 4377
F: +44(0)131 451 3129
E: g.m.seed@hw.ac.uk
U: http://www.hw.ac.uk/mecWWW/research/staff/gms.htm