On Jul 11, 2008, at 1:52 PM, Steven Watanabe wrote:

f3 takes 3 arguments, so you need to pass a third argument to bind. F2arg f2 = bind<double>( f3, _1, x2, _2);

f2(5, 6) // calls f3(5.0, x2, 6.0)

What if I wanted to do something like: int main() { using namespace boost; using namespace lambda; typedef function< double() > F0arg; const double x1=1.1, x2=2.2; F0arg f = bind( ret<double>(_1*_2)(x1,x2) ); } Or, slightly more generally, if we want to bind other boost::function objects and not POD: typedef function< double(T) > Func; Func func1, func2; ... F0arg f = bind( ret<double>(_1*_2)(func1,func2) ); Any ideas here?

Does this work? using namespace boost::lambda; F0arg f = bind(protect(_1*_2), bind(func1), bind(func2));

In Christ, Steven Watanabe

I tried the following (the simple case), and it would not compile: int main() { using namespace boost::lambda; typedef boost::function< double() > F0arg; const double x1=1.1, x2=2.2; F0arg f = bind(protect(_1*_2), bind(x1), bind(x2)); }

#include #include #include

int main() { using namespace boost::lambda; typedef boost::function< double() > F0arg; boost::function< double() > arg1, arg2; const double x1=1.1, x2=2.2; F0arg f = bind(protect(_1*_2), x1, x2); boost::function< double() > func1(f), func2(f); F0arg f2 = bind(protect(_1*_2), bind(func1), bind(func2)); }

Any explanation as to why this works and the previous example does not? It seems that the line of code:

boost::function< double() > func1(f), func2(f); is redundant with F0arg f = bind(protect(_1*_2), x1, x2); isn't it? (Clearly not, since it compiles while the earlier version did not)

Jame

I know I am probably trying patience of the readers here, but I have one more question. Suppose I have something like typedef boost::function< double(double) > F1; F1 f; F1 g; and I want to create a function that takes a single argument "t" and produces f(t)*g(t). I can create the multiply function as boost::function mult(_1*_2); But now how do I create a "F1" function "h" such that h(t) = f(t)*g(t)? I want to do something like: F1 h = bind( mult, f, g, _1 ); or F1 h = bind( mult, bind(f,_1), bind(g,_1), _1 ); but these aren't working... Any tips would be greatly appreciated... James

James Sutherland:

I can create the multiply function as

boost::function mult(_1*_2);

But now how do I create a "F1" function "h" such that h(t) = f(t)*g(t)?

bind( mult, bind( f, _1 ), bind( g, _1 ) ) creates h(t) = mult( f(t), g(t) ).

I want to do something like:

F1 h = bind( mult, f, g, _1 );

This creates h(t) = mult( f, g, t ).

or

F1 h = bind( mult, bind(f,_1), bind(g,_1), _1 );

This creates h(t) = mult( f(t), g(t), t ). _1 represents the first free argument, 't' in your notation.