Upper Case to Lower Case

[Freakzoyd]

Hello guys, i am a beginner at programing, and I found this site really helpful as it has c++ tutorials, all the libraries and its functions with example code, and the forums. I been trying to change upper case letters to lower case, first i did it with type casting and the ASCII code, but I found that it was possible with the library ctype, but I don't understand any of the example codes, are they in C? I program in bloodshed dev-C++.

Program with type casting:

#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    char A[10];
    int largo, sum=0;
    for (int a=1; A[a-1]!='\n'; a++){
        cin.get(A[a]);
        largo=a;
        if (int (A[a])>=65 and int (A[a])<=90){
                A[a]=int (A[a])+32;
                sum+=int (A[a]);
        }
    }
    cout<<endl;
    cout<<"Sum: "<<sum<<endl;
    string trash;
    getline(cin, trash); 
    getline(cin, trash);
    return EXIT_SUCCESS;
}

Program with the library Cstring:

#include <cstdlib>
#include <iostream>
#include <cctype>
#include <cstring>

using namespace std;

int main(int argc, char *argv[])
{
    char A[20];
    cin>>A;
    cout<<endl;
    for (int b=0; b<=strlen(A); b++){
        tolower(A[b]);
        cout<<A[b];
    }
    cout<<endl;
    string trash;
    getline(cin, trash); 
    getline(cin, trash);
    return EXIT_SUCCESS;
}

My questions are: what do u recomend me to understand the examples that are around the libraries explanation? make the tutorials? Because i program differently from the examples; and how can I change upper to lower case letters using the ctype library, using tolower?

[phoenix111]

Not sure what's ur doubt.
You already have what you want:

Just include this librabry <cctype>
and when you want to change the case of any character,simply use tolower and toupper function and pass that character as an argument.

[Skillless]

Yes, the examples are in C++

And i recommend you to read through the whole tutorial on this site, it has lots of examples also

[Freakzoyd]

My doubt is that in the second code, the tolower doesn't work and i have the cctype library; any idea why?

[filipe]

std::tolower doesn't write into the variable, it just returns the lower case character value for the character you pass to it.

[Galik]

Your loop goes too far and you didn't assign the modified letter back to the char array:

#include <cstdlib>
#include <iostream>
#include <cctype>
#include <cstring>

using namespace std;

int main(int argc, char *argv[])
{
    char A[20];
    cin>>A;
    cout<<endl;
//    for (int b=0; b<=strlen(A); b++) // loops too far
    for (int b=0; b < strlen(A); b++) // b < strlen(A) is correct
    {
//    	tolower(A[b]); // this doesn't change the value
    	A[b] = tolower(A[b]); // need to assign the output of tolower()
        cout<<A[b];
    }
    cout<<endl;
    string trash;
    getline(cin, trash);
    getline(cin, trash);
    return EXIT_SUCCESS;
}

Also you might want to look at the std C++ libraries for this too:

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

int main()
{
	std::string str = "Just Some Text";

	std::transform(str.begin(), str.end(), str.begin(), std::ptr_fun(tolower));
	std::cout << str << std::endl;

	std::transform(str.begin(), str.end(), str.begin(), std::ptr_fun(toupper));
	std::cout << str << std::endl;
}