A replacement for std::bind2nd

Question

I have a foo which is a std::vector. It represents the \"edge\" values for a set of ranges.

For example, if foo is

Answer 1

In C++11, you can use std::bind; it just isn't as obvious how to use it:

#include 
using namespace std::placeholders;
std::find_if(
    foo.begin(),
    foo.end(),
    // create a unary function object that invokes greater::operator()
    // with the single parameter passed as the first argument and `bar` 
    // passed as the second argument
    std::bind(std::greater(), _1, bar)
) - foo().begin() - 1;

The key is the use of the placeholder argument, which are declared in the std::placeholders namespace. std::bind returns a function object that takes some number of parameters when it is invoked. The placeholders used inside the call to std::bind show how the arguments provided when the resulting object is invoked map to the argument list to the callable that you're binding to. So, for instance:

auto op1 = std::bind(std::greater(), _1, bar);
op1(5); // equivalent to std::greater()(5, bar)

auto op2 = std::bind(std::greater(), bar, _1);
op2(5); // equivalent to std::greater()(bar, 5)

auto op3 = std::bind(std::greater(), _2, _1);
op3(5, bar); // equivalent to std::greater()(bar, 5)

auto op4 = std::bind(std::greater(), _1, _2);
op4(5, bar); // equivalent to std::greater()(5, bar)