Is there an easy way to change lowercase to uppercase using ascii codes in c++?

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Hi
I'm hoping to find a way to change any lowercase letter to an uppercase no matter which letter is used. I saw online something about using the asciii values to accomplish this however I'm not sure how this would be applied to every letter.

This I believe will convert lowercase b to uppercase B, but how could I change this
to apply to any letter?
‘B’ = ‘b’ – ‘a’ + ‘A’

I greatly appreciate any advice or help you may offer.

Posted 10-Oct-13 5:16am

CAS1224

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Philippe Mori 11-Oct-13 20:51pm

You should avoid doing that as it only works for characters between a and z (when using ASCII code page). It won't works for accentued characters and it won't follows current language rule when rule differes from language to language.

In any real life application, you want to use functions that take into account code page (437, 1252, Unicode), encoding (like UTF-8), selected language rules (English, French, Spanish...). Same thing wouls apply to sorting. Rules are diffeents depending on the language.

3 solutions

Solution 4

The safe way is to do something like:

C++

char c = ...;
if (islower(c)) c=toupper(c);

or

C++

wchar_t c = ...;
if (iswlower(c)) c=towupper(c);

See also http://www.cplusplus.com/reference/cctype/islower/[^] for char based text, or http://www.cplusplus.com/reference/cwctype/iswlower/[^] for wchar_t based text.
Cheers
Andi

Posted 10-Oct-13 8:15am

Andreas Gieriet

Updated 10-Oct-13 8:16am

v2

Comments

Philippe Mori 11-Oct-13 20:45pm

No really necessary to check if it is a lowercase character first as it might almost double execution time.

Andreas Gieriet 11-Oct-13 23:06pm

Yes, you are right. The toupper/tolower and its siblings already check for the appropriate range.
Cheers
Andi

Solution 3

You can use these functions[^] or these[^]. Or simply subtract hex 20 (decimal 32) like:

C++

char lowerChar = 'b';
char upperChar = lowerChar - 0x20;

NB you should check first that the character is lower case as described in the documentation links above.

Posted 10-Oct-13 6:40am

Richard MacCutchan

Updated 10-Oct-13 6:42am

v2

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greg19 · Accepted Answer · 2013-10-10T05:32:00

Solution 1

The difference between the ASCII value for A (65) and a (97) is 32. This is the same for all letters. You can simply subtract 32 from the lower case value and that would be the upper case equivalent.

Posted 10-Oct-13 5:32am

greg19

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CAS1224 10-Oct-13 11:59am

Thanks for the explanation it helps a lot.