How to Convert a C++ String to Uppercase - c++

Question

I need to convert a string in C++ to full upper case. I've been searching for a while and found one way to do it:
#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int main()
{
string input;
cin >> input;
transform(input.begin(), input.end(), input.begin(), toupper);
cout << input;
return 0;
}
Unfortunately this did not work and I received this error message:
no matching function for call to 'transform(std::basic_string::iterator, std::basic_string::iterator, std::basic_string::iterator,
I've tried other methods that also did not work. This was the closest to working.
So what I'm asking is what I am doing wrong. Maybe my syntax is bad or I need to include something. I am not sure.
I got most of my info here:
http://www.cplusplus.com/forum/beginner/75634/
(last two posts)

Answer 1

You need to put a double colon before toupper:
transform(input.begin(), input.end(), input.begin(), ::toupper);
Explanation:
There are two different toupper functions:
toupper in the global namespace (accessed with ::toupper), which comes from C.
toupper in the std namespace (accessed with std::toupper) which has multiple overloads and thus cannot be simply referenced with a name only. You have to explicitly cast it to a specific function signature in order to be referenced, but the code for getting a function pointer looks ugly: static_cast<int (*)(int)>(&std::toupper)
Since you're using namespace std, when writing toupper, 2. hides 1. and is thus chosen, according to name resolution rules.

Answer 2

Boost string algorithms:
#include <boost/algorithm/string.hpp>
#include <string>
std::string str = "Hello World";
boost::to_upper(str);
std::string newstr = boost::to_upper_copy("Hello World");
Convert a String In C++ To Upper Case

Answer 3

Try this small program, straight from C++ reference
#include <iostream>
#include <algorithm>
#include <string>
#include <functional>
#include <cctype>
using namespace std;
int main()
{
string s;
cin >> s;
std::transform(s.begin(), s.end(), s.begin(), std::ptr_fun<int, int>(std::toupper));
cout << s;
return 0;
}
Live demo

Answer 4

You could do:
string name = "john doe"; //or just get string from user...
for(int i = 0; i < name.size(); i++) {
name.at(i) = toupper(name.at(i));
}

Answer 5

Uppercase to Lowercase and viceversa using BitWise operators
1.
string s = "cAPsLock";
for(char &c: s)
c = c | ' '; // similar to: c = tolower(c);
cout << s << endl; // output: capslock
string s = "cAPsLock";
for(char &c: s)
c = c & ~' '; // similar to: c = toupper(c);
cout << s << endl; // output: CAPSLOCK
PS: for more info check this link

Answer 6

#include <iostream>
using namespace std;
//function for converting string to upper
string stringToUpper(string oString){
for(int i = 0; i < oString.length(); i++){
oString[i] = toupper(oString[i]);
}
return oString;
}
int main()
{
//use the function to convert string. No additional variables needed.
cout << stringToUpper("Hello world!") << endl;
return 0;
}

Answer 7

Like leemes said, you can use toupper(int). Like this:
void ToUpper(string &str) {
for (auto beg = str.begin(); beg != str.end(); ++beg) {
*beg = toupper(*beg);
}
}
It'll through in each character from str and convert it to upper. Example:
int main()
{
string name;
cout << "Insert a name: ";
cin >> name;
ToUpper(name);
cout << "Name in upper case: " << name << endl;
}

Answer 8

You can also use the function from code below to convert it to Upper-case.
#include<iostream>
#include<cstring>
using namespace std;
//Function for Converting Lower-Case to Upper-Case
void fnConvertUpper(char str[], char* des)
{
int i;
char c[1 + 1];
memset(des, 0, sizeof(des)); //memset the variable before using it.
for (i = 0; i <= strlen(str); i++) {
memset(c, 0, sizeof(c));
if (str[i] >= 97 && str[i] <= 122) {
c[0] = str[i] - 32; // here we are storing the converted value into 'c' variable, hence we are memseting it inside the for loop, so before storing a new value we are clearing the old value in 'c'.
} else {
c[0] = str[i];
}
strncat(des, &c[0], 1);
}
}
int main()
{
char str[20]; //Source Variable
char des[20]; //Destination Variable
//memset the variables before using it so as to clear any values which it contains,it can also be a junk value.
memset(str, 0, sizeof(str));
memset(des, 0, sizeof(des));
cout << "Enter the String (Enter First Name) : ";
cin >> str; //getting the value from the user and storing it into Source variable.
fnConvertUpper(str, des); //Now passing the source variable(which has Lower-Case value) along with destination variable, once the function is successfully executed the destination variable will contain the value in Upper-Case
cout << "\nThe String in Uppercase = " << des << "\n"; //now print the destination variable to check the Converted Value.
}