toupper() & tolower() problem?

The following code converts the string copied to uppercase and then to lowercase again.

Code:

// Convert a string to uppercase & lowercase

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

using namespace std;

int main()
{
 char str[80];
 int i;
 
 strcpy(str, "This is copied to str");
 for(i=0;str[i];i++)
                    str[i]=toupper(str[i]);
 cout << str;
 
 for(i=0;str[i];i++)
                    str[i]=tolower(str[i]);
 
 cout << "\nOriginal str was ( " << str << " )\n\n";
 
system("pause");
return 0;

}

The problem is I cannot make it work without a second for loop. I don't want to use the second for loop, instead any other way if possible.

I don't really sure about what am I thinking..
why don't you use, strupper and strlower?

Well it would be very useful if you show me how to do it, as I am a beginner in C++. I have not used strupper and strlower before.

Well the problem lies with your second condition of for loop

it should be i < strlen(str)

your modified code will be like this

Code:

 for(i=0; i < strlen(str); i++)

If you're willing to make more copies of the original string, you can just copy a lowercase version and an uppercase version, all using one loop.

Originally Posted by whiteflags

If you're willing to make more copies of the original string, you can just copy a lowercase version and an uppercase version, all using one loop.

that is one point of optimization and others what i can suggest use ++i instead of i++ and user memset.

None of those things are optimizations, and even if they were, strlen being called every iteration makes it irrelevant.

Originally Posted by whiteflags

None of those things are optimizations, and even if they were, strlen being called every iteration makes it irrelevant.

I don't know how can u say that

for post and pre increment

"preincrement (++i) adds one to the value of i, then returns i; in contrast, i++ returns i then adds one to it, which in theory results in the creation of a temporary variable storing the value of i before the increment operation was applied". And it means pre increment is better than the post one

Guys can't we use the transform function here like the one used in the following code?

Code:

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

int main()
{
    char string[100];
    char upString[100];
    char lowString[100];
    
    strcpy(string, "I have a nice red house and you're not gonna take it from me!");
    
    unsigned int stringLength = 0;
    for (unsigned int i = 0; string[i] != '\0'; i++)
        stringLength++;
    
    std::cout << "The original: " << string << "\n\n";
    std::cout << "Now applying transform() to uppercase...\n\n";
    
    std::transform(&string[0], &string[stringLength], &upString[0], toupper);
// This is equal to
// std::transform(string, string + stringLength, upString, toupper);
// but might make more sense
    upString[stringLength] = 0;
    
    std::cout << "upString: " << upString << "\n\n";
    std::cout << "Now applying transform() to lowercase (it's a verb, yes)...\n\n";
    
    std::transform(&string[0], &string[stringLength], &lowString[0], tolower);
    lowString[stringLength] = 0;
    
    std::cout << "lowString: " << lowString << "\n\n";
    
    system("pause");
    return 0;
}

>> i dont know how you can say that

What do you think takes more time, counting the number of characters in the string or copying a single integer? Now square that estimate, because you called it for every iteration. Thinking in theory is fine, but you should use common sense first.

>> Guys can't we use the transform function here like the one used in the following code?

What do you think

Originally Posted by RockyMarrone

I don't know how can u say that

for post and pre increment

For simple types like ints, the compiler would optimize i++ to ++i for you anyways, but yes, I always use ++i in for loops anyways.

Yes, we should prefer ++i to i++.

No, we should not prefer one over the other. It is a matter of style and where one form fits better than the other. Neither is better than the other.

I see. Thank you.

It matters for non-pointer iterators, so it's a good habit to use ++i, so that ++itr is consistent.

Re:the OP
Just have a seperate buffer for the uppercase and lowercase strings.