C++ Checking String

Question

Say I am taking a string in and want to check whether or not it has a capital letter in the string. I input the string from a file. How would I go about breaking it down to check to see if it has an uppercase value using the ascii values? Thanks!

Answer 1

You can use the C++ algorithm library to find if a string contains an uppercase value in it by using a predicate (using a wrapper version of std::isupper):

#include <algorithm>
#include <iostream>
#include <string>
#include <cctype>

bool IsUpper (char c) {
    return std::isupper(c);
}

bool hasUpperCase (std::string str) {
    std::string::iterator it = std::find_if(str.begin(), str.end(), IsUpper);
    if (it != str.end()) {
        return true;
    }
    else {
        return false;
    }
}

int main() {
    std::string s = "This contains an uppercase character in it...";
    if (hasUpperCase(s)) {
        std::cout << "String s contains a least one uppercase character." << std::endl; 
    }
    else {
        std::cout << "String s does not contain any uppercase character." << std::endl; 
    }
}

From here a predicate is:

is a C++ function returning boolean or instance of object having bool operator() member. Unary predicate take one agrument, binary - two, etc. Examples of questions predicate can answer for particular algorithm are:

• Is this element is what we are looking for?
• Is the first of two arguments is ordered first in our order?
• Are the two arguments equal?

Almost all STL algorithms take predicate as last argument.

So, in summary, this works by each character in the string against the predicate function: IsUpper which itself uses std::isupper to do the checking to see if the character in question is uppercase or not. If it is, it returns true, and that character is stored in the iterator.

REFERENCES:

http://en.cppreference.com/w/cpp/algorithm/find https://stackoverflow.com/a/5921826/866930