Using boost to create a lambda function which always throws
Is it possible to create an inline lambda using boost which always throws an exception?
(this question follows on from "Using boost to create a lambda function which always returns true").
Suppose I have a function which takes some form of predicate:
void Foo( boost::function<bool(int,int,int)> predicate );
If I want to call it with a predicate that always throws an exception, define a helper function:
bool AlwaysThrow( int, int, int ) { throw std::exception(); }
...
Foo( boost::bind( A开发者_如何学编程lwaysThrow ) );
But is there anyway to call this function (possibly using boost::lambda) without having to define a separate function?
(Note 1: I can't use C++0x.)
(Note 2: I've simplified this example. My actual "predicate" function doesn't return a bool, it returns a type which doesn't have a default-ctor.)
There is a throw_exception
function in Boost.Lambda.
For example:
#include <boost/lambda/lambda.hpp>
#include <boost/lambda/exceptions.hpp>
#include <boost/function.hpp>
#include <exception>
#include <iostream>
struct Bar {
private:
Bar() {}
};
void Foo(boost::function<Bar(int,int,int)> predicate) {
std::cout << "should show" << std::endl;
predicate(1,2,3);
std::cout << "should not show" << std::endl;
}
int main () {
Foo( boost::lambda::ret<Bar>(boost::lambda::throw_exception( std::exception() ) ) );
return 0;
}
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