Can someone please explain to me how I can fix this error I'm getting:

error: 's' was note declared int this scope

digits[i] = s.length() - '0'; ^

Here is my code:

BigInt::BigInt(string s) { if(s.length() > 100){ cout << "Size can't exceed 100!"; exit(1); } }

int BigInt::getLen() const { int i; for (i = 0; i < 100; i++) { digits[i] = s.length() - '0'; } len = s.length(); return len; }