For some reason this lambda statement doesn't want to compile:
bool DepthFirstSearch = [](Graph *g, bool *ch, stack<int> &S, int v, int w) -> bool
{
//Here is recursive DFS code
};
with the error: no suitable conversion function from: "lambda[]bool()->bool" to bool exists.
My question is why?
The type of the lambda isn't bool. You could use auto to make this work
auto DepthFirstSearch = [](Graph *g, bool *ch, stack<int> &S, int v, int w) -> bool { ... }
or use std::function to specify the return type explicitly, but that would be quite cumbersome. See http://en.cppreference.com/w/cpp/utility/functional/function.
Generally it is easier to just use auto, otherwise you'd have to change the type of the variable every time you change the parameters of the lambda.
If you want to make it recursive, then you have to capture the lambda (by ref). To do that, you need to give it a named type:
std::function<bool(Graph*, bool*, stack<int>&, int, int)> DepthFirstSearch =
[&](Graph *g, bool *ch, stack<int> &S, int v, int w) {
// bunch of code here that possibly calls DepthFirstSearch
};
You can't just do auto DepthFirstSearch = [=](...){...} here because the lambda will need to know the type of DepthFirstSearch in order to capture it - and if you just use auto then the type won't exist until after the lambda-expression is processed, which is too late. Hence the std::function<...>.
(...);(with the arguments for the call) at the end (after the}) to actually call it. If you want to store it, to call it later, useauto DepthFirstSearch = [](..)...;boolvalue with a lambda expression. Did you mean to invoke the lambda at the end of that expression ([](...) -> bool {...}(<arguments go here>))?