C++ Function bind repeating arguments to curried function

Question

I am trying to understand the concept of currying and calling a function which concats three strings but by passing only two strings and using the second argument twice.

Answer 1

Copying strings is expensive. Since std::bind thinks that the values of the placeholders are only used once, it performs a std::move on the strings. This is done for each Parameter and as a consequence, either b or c is a moved, that means empty string.

You can change that behavior by explicitly saying what you mean, by passing the arguments by const-reference:

string concatthreestrings(string const& a,string const& b,string const& c)

Now, it should work.