Discussion on: Overly Functional C++: The Fold

// Fold a binary operation over a vector
template <typename T>
T fold(std::vector<T> nums, T acc, std::function<T(T, T)> func)
{
    int length = nums.size();
    if (length == 0)
    {
        return acc;
    }
    else
    {
        int newAcc = func(acc, nums[0]);
        std::vector<T> newInput(nums.begin() + 1, nums.end());
        return fold(newInput, newAcc, func);
    }
}

// ..

int main()
{
// ..
int result = fold(nums, acc, [](int acc, int curr) { return acc + curr; });
// ..
}

foldsum.cpp:12:3: note:   template argument deduction/substitution failed:
foldsum.cpp:62:78: note:   'main()::<lambda(int, int)>' is not derived from 'std::function<T(T, T)>'
   62 |     int result = fold(nums, acc, [](int acc, int curr) { return acc + curr; });