Computer Science Canada

Help with conversion to lower case
Author:  Colliflower [ Wed Nov 02, 2011 8:57 pm ]
Post subject:  Help with conversion to lower case
I am trying to convert the letters of a string to lower case using a for loop and the tolower command, but i am getting an error...

#include <iostream>
#include <ctype.h>
#include <string>
using namespace std;
int main () {
std::string sDecision, sWord;
cout << "Hello! Would you like to move your letter up, or down?";
cin >> sDecision;
sWord= "";
for (int num = 0; num < sDecision.size(); num++) {
//Error occurs saying cannot convert from char to const char
sWord.append(char(tolower(sDecision[num])));
}
cout << sWord << "\n";
system("PAUSE");
return 0;
}

I have tried multiple things, but i cannot get this to work Sad please help
Author:  Tony [ Wed Nov 02, 2011 10:06 pm ]
Post subject:  Re: Help with conversion to lower case
Colliflower @ Wed Nov 02, 2011 8:57 pm wrote:
I have tried multiple things

what kind of things have you tried?
Author:  Colliflower [ Wed Nov 02, 2011 10:16 pm ]
Post subject:  Re: Help with conversion to lower case
at first i was appending the letters by calling them strings but my teacher said i should try using characters instead, I was mainly just trying whatever came to mind but the period ran out before i could figure out the problem and continue the question (I am kinda new to c++ so i am not entirely sure what I can and cannot do...)
Author:  Tony [ Wed Nov 02, 2011 10:48 pm ]
Post subject:  Re: Help with conversion to lower case
Colliflower @ Wed Nov 02, 2011 8:57 pm wrote:
//Error occurs saying cannot convert from char to const char

well char and const char are different types...
Author:  S_Grimm [ Thu Nov 03, 2011 9:08 am ]
Post subject:  Re: Help with conversion to lower case
http://www.cplusplus.com/reference/clibrary/cctype/tolower/

give that function a try.

Remember that strings are just arrays of characters and can be accessed just like an array.

edit: try going through each character in the string and calling to lower, then passing it into an output string.
Author:  Colliflower [ Thu Nov 03, 2011 4:14 pm ]
Post subject:  Re: Help with conversion to lower case
S_Grimm @ Thu Nov 03, 2011 9:08 am wrote:
http://www.cplusplus.com/reference/clibrary/cctype/tolower/

give that function a try.

Remember that strings are just arrays of characters and can be accessed just like an array.

edit: try going through each character in the string and calling to lower, then passing it into an output string.


That is what i am trying to do, I am going through each character of the string sDecision and use the tolower command on each letter and then append it to the sWord string. I don't know what I am doing wrong though...

Tony @ Wed Nov 02, 2011 10:48 pm wrote:

well char and const char are different types...

I am not sure where i am using the const char though, I know what a const char is, I just don't see where I am using one...
Author:  Tony [ Thu Nov 03, 2011 5:25 pm ]
Post subject:  RE:Help with conversion to lower case
check your function signatures, one is probably expecting a different type than you are providing.

...
Also, the actual error is different from what you posted:
Quote:

test.cc:12: error: invalid conversion from ?char? to ?const char*?
test.cc:12: error: initializing argument 1 of ?std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, _Traits, _Alloc>::append(const _CharT*) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]?

Emphasis mine. The problem is that string.append is expecting const char* (not const char as you've said), while you are giving it just char.
Author:  Colliflower [ Thu Nov 03, 2011 6:03 pm ]
Post subject:  Re: Help with conversion to lower case
Thanks Tony i had to change a lot of things because I got new errors every time I tried fixing the old ones Mad
I ended up with this as a fix
Quote:
#include <iostream>
#include <ctype.h>
#include <string>
using namespace std;
int main () {
string sDecision;
int iSize;
cout << "Hello! Would you like to move your letter up, or down?";
cin >> sDecision;
iSize = sDecision.size();

for (int num = 0; num < iSize; num++) {
sDecision[num] = ((tolower(sDecision[num])));
}
cout << sDecision << "\n";
system("PAUSE");
return 0;
}


Thanks again for helping out the noobie!

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