Tolower function

[beck2]

Hello everyone its Angela again. Can anyone help me please?
i want to convert uppercase characters to lower case using the <stdlib.h>
and the function tolower. for example i want to display "HELLO" to lower.

my code is:

#include<iostream.h>
#include<stdlib.h>

void main() {

cout<<tolower("HELLO");


}

i get the error : implicit declaration of function int to lower(.....)


what am i doing wrong?

[Banfa]

Not including ctype.h

[horace1]

As indicated by Banfa you need to include the appropriate header but also the function tolower() takes a single character (Iint) as a parameter and returns the corresponding lowercase letter (int), i.e.

     int tolower(int c);
 

so you have to have a loop changing each character in turn, e.g.

#include<iostream>
#include<cctype>        // for tolower()
using namespace std;
 
int main() {
    char upper[]="HELLO", lower[10]={0};
    int i;
    for(i=0; i<strlen(upper); i++)
       lower[i] = tolower(upper[i]);  // convert each character
    cout<< lower << endl;
    cin.get();
}
 

if you are using a string you can use the transform() function
http://www.josuttis.com/libbook/string/iter1.cpp.html

e.g.

#include<iostream>
#include<cctype>        // for tolower()
#include <algorithm>
using namespace std;
 
int main() {
    string s("HELLO");
    transform(s.begin(), s.end(), s.begin(), (int(*)(int))std::tolower);
    cout<< s << endl;
    cin.get();
}
 

[Ganon11]

As indicated by Banfa you need to include the appropriate header but also the function tolower() takes a single character (Iint) as a parameter and returns the corresponding lowercase letter (int), i.e.

     int tolower(int c);
 

so you have to have a loop changing each character in turn, e.g.

#include<iostream>
#include<cctype>        // for tolower()
using namespace std;
 
int main() {
    char upper[]="HELLO", lower[10]={0};
    int i;
    for(i=0; i<strlen(upper); i++)
       lower[i] = tolower(upper[i]);  // convert each character
    cout<< lower << endl;
    cin.get();
}
 

I am fairly certain that you will have to use a static_cast statement when assigning values to lower. Since tolower(int) returns an integer, it must be cast to a character value. The statement

lower[i] = tolower(upper[i]);

should be changed to

lower[i] = static_cast<char>(tolower(upper[i]));