Bill Woessner wrote:
I'm trying to replace a loop with a call to std::generate and I'm
about at wits end. Here's the working code:
std::vector<double>::iterator it;
std::vector<doubledata(100);
RandomGenerator<doubleg;
for(it = data.begin(); it != data.end(); ++it)
{
*it = g.GetGaussian();
}
This works fine. So I thought I could use std::generate to accomplish
the same thing. I've tried lots of combinations, but this is the one
I thought most likely to work:
std::generate(data.begin(), data.end(),
std::bind1st(std::mem_fun(&RandomGenerator<double> ::GetGaussian),
&g));
I thought this should work because GetGaussian effectively has one
parameter, namely the object it's being invoked on. However, when I
try to compile this, I get a slew of errors about first_argument_type
and second_argument_type not being defined.
Any thoughts?
'binder1st' inherits from 'unary_function' accepting the second argument
of the function it binds. Since in your case the second argument doesn't
exist (it's 'void'), 'mem_fun' does not provide it, so it becomes missing
AFA 'binder1st' is concerned...
You would be better off using advanced binders from Boost, or providing
a simple operator() instead of 'GetGaussian' (or wrapping 'GetGaussian'
yourself).
template<class Tstruct RandomGenerator {
T GetGaussian() const { return 42.; }
// other methods
};
template<class Tstruct GaussianWrapper_t {
RandomGenerator<Tg;
GaussianWrapper_t(RandomGenerator<Tconst& g) : g(g) {}
T operator()() const {
return g.GetGaussian();
}
};
template<class T>
GaussianWrapper_t<TGaussianWrapper(RandomGenerator <Tconst& g)
{
return GaussianWrapper_t<T>(g);
}
int main()
{
std::vector<double>::iterator it;
std::vector<doubledata(100);
RandomGenerator<doubleg;
std::generate(data.begin(), data.end(), GaussianWrapper(g));
}
V
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