Thread: toUpper

Morning,

with this program, I prompt the user to enter a character and if it is a lower case letter, it would return its uppercase value.

Here is my code:

Code:

int toUpper(int x);

main()
{
	char c;
	
	printf("Enter character: ");
	scanf("%c", &c);

	printf("Uppercase = %c\n", toUpper(c));	
}

int toUpper(int x)
{
	char upper;

	if(x >= 'a' && x <= 'z')
	{
		upper = x - 32;
		  return upper;
	}

}

It definitely works for lowercase letters. But for some reason, conditions that doesn't fit the boolean expression

Code:

if(x >= 'a' && x <= 'z');

still would execute.

For instance here are two sampled runs:

Code:

Enter character: b
Uppercase = B

Code:

Enter character: B
Uppercase = "

B in decimal is 66 and " in decimal is 34 which 66 - 34 = 32, which shows that it executes. Is there an error in my boolean expression that allows this to happen? I even tried changing the conditions to decimal values but still produces the same outcome.

Originally Posted by claudiu

So maybe pass c as a char not an int to the function.

Tried that as well. Same result :/

Try to return x at the bottom of the function, if the function is receiving an upper case letter it returns nothing.

Originally Posted by Subsonics

Try to return x at the bottom of the function, if the function is receiving an upper case letter it returns nothing.

The problem is that it's returning a value for all sorts of characters. Here's another sample run:

Code:

Enter character: _
Uppercase = ?

the decimal for '_' underscore is 95
the decimal for '?' question mark is 63

which is the difference of 32.

Originally Posted by aromash

The problem is that it's returning a value for all sorts of characters. Here's another sample run:

Code:

Enter character: _
Uppercase = ?

the decimal for '_' underscore is 95
the decimal for '?' question mark is 63

which is the difference of 32.

Compile with warnings on (-Wall in GCC) and you get a:

"warning: control reaches end of non-void function"

It is undefined behavior afaik if not c99, so, it will return anything it feels like.

You need to preset upper to the character so that it returns it if it's already upper case.

Code:

int toUpper(char x)
{
	char upper = x;

	if(x >= 'a' && x <= 'z')
	{
		upper = x - 32;
	}
     return upper;
}

Strictly speaking it's not needed, what is needed is to return something instead of relying on chance. This would work equally well for example.

Code:

int toUpper(int x)
{
        char upper;

        if(x >= 'a' && x <= 'z')
        {
                upper = x - 32;
                return upper;
        }
        return x;
}

Or this for that matter.

Code:

int toUpper(int x)
{
        if(x >= 'a' && x <= 'z')
                return x-32;
        return x;
}

i think it is more easy to use the toupper() function to get the result you want.

The code you posted in post#1 should work for ascii char set.
But the reason it does not work is because you are not returning anything if condition is false.
Your compiler should give you warning. It seems like you are not paying attention to them...

Originally Posted by Subsonics

Strictly speaking it's not needed, what is needed is to return something instead of relying on chance. This would work equally well for example.

Code:

int toUpper(int x)
{
        char upper;

        if(x >= 'a' && x <= 'z')
        {
                upper = x - 32;
                return upper;
        }
        return x;
}

Or this for that matter.

Code:

int toUpper(int x)
{
        if(x >= 'a' && x <= 'z')
                return x-32;
        return x;
}

Yep... lots of ways to do this one, that's for sure.

i think it is more easy for you to use the function toupper() in ctype.h to do what you want. try it, friend.