Warning
This depends on #37. Wish GitHub had some stacked diff capability.
% clang++ -std=c++20 tests/c++/missing-hash.cpp |& cwhy --llm gpt-4
The problem is that `std::hash` does not provide a specialization for
`std::pair<int, int>`. This means that you can't use `std::hash` with
`std::pair<int, int>`, hence the error. As a result, when you declare
an `std::unordered_set<std::pair<int, int>>`, the compiler is trying
to create an `std::hash<std::pair<int, int>>`, and failing because it
doesn't exist.
You could define a custom hash function for `std::pair<int, int>` and
use it in your `std::unordered_set`.
Here's an example:
```c++
struct pair_hash {
template <class T1, class T2>
std::size_t operator () (const std::pair<T1, T2> &pair) const {
return std::hash<T1>()(pair.first) ^ std::hash<T2>()(pair.second);
}
};
std::unordered_set<std::pair<int, int>, pair_hash> visited;
In this code, pair_hash is a functor that computes a hash value for
std::pair<int, int> objects. This hash function is then used in the
std::unordered_set declaration.
In this code,
pair_hash
is a functor that computes a hash value forstd::pair<int, int>
objects. This hash function is then used in thestd::unordered_set
declaration.This request cost ~ 0.12$.