C++ atof invalid use of void bug

Question

Please Help I'm so close to finishing this huge project. I don't understand an error I'm receiving

score-=(double)atof(kitty.pop_front());

!invalid use of void expression

kitty is a deque type string. Score is a long double. I'm not good with type conversions but the error seems really unrelated?

I tried other forum's solutions but they are all relatively unrelated.

Answer 1

dequeue::pop_front() returns void:

void pop_front();

So you can't use it in an expression that way.

You could instead do:

score-=(double)atof(kitty.front().c_str());
kitty.pop_front();

Answer 2

If the value in the deque is std::string , the atof function call should be:

score -= atof(kitty.front().c_str());

The reason is that atof expects a const char* parameter, and std::string::c_str() returns a const char* that represents the string.

Second, the front() function returns the value that is at the front of the deque. If you want to remove the value from the front , then you call kitty.pop_front() .