Re: Is there an STL algo to fill a vector with product of 2 other
vectors?
On Dec 9, 10:55 am, Steve555 <foursh...@btinternet.com> wrote:
On 9 Dec, 15:27, Pete Becker <p...@versatilecoding.com> wrote:
On 2008-12-09 09:43:51 -0500, Steve555 <foursh...@btinternet.com> said:
I've looked through the list of algorithms and there doesn't appear t=
o
be one.
transform() is the closest, but alas works on only a single vector.
There are two versions of transform. One works on a single input range
and the other works on two input ranges. The latter sounds like just
what you need.
--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)
Thanks Pete, hadn't spotted the second version.
I have a simple example working with multiplies<int>()
, but what about an arbitrary functor, how do I declare the arguments?
e.g: (where in1, in2, out, are my 3 vectors)
See:
http://www.sgi.com/tech/stl/transform.html
Specifically, your functor must follow this:
http://www.sgi.com/tech/stl/BinaryFunction.html
For example:
template <typename T> bool equals (const T &a, const T &b) {
return a == b;
}
void somewhere () {
std::vector<int> x, y;
x.push_back(1);
x.push_back(2);
y.push_back(2);
y.push_back(2);
std::vector<bool> result(x.size());
std::transform(x.begin(), x.end(), y.begin(), result.begin(),
equals<int>);
assert(result[0] == false);
assert(result[1] == true);
}
void pointlessCalc(in1, in2, out)
{
out = (in1 + 1) * (in2 +2);
}
You'd want to return the value:
out pointlessCalc (in1, in2);
Jason