Thread: the entered character is a lowercase, uppercase, or a real number

Please x 20 do NOT rely on ASCII. Don't mention it. Don't assume it is used. Don't even think about it.
The C++ standard does not guarantee what the "underlying character set" is. It could be ASCII, but it could also be something entirely different.
Furthermore, ASCII is an old american-only system. It needs to go away. Unicode is the new future as it is now.
So again, don't assume ASCII, and throw away your ASCII table.

Thanks a lot, laserlight. It was helpful.

Originally Posted by laserlight

Incidentally, though it does not matter in practice these days, in theory the English letters in the character set need not be in contiguous and in alphabetical order. You do have this guarantee of order and contiguous placement for the digits though.

If it doesn't really have English alphabet in contiguous manner, then how would it work? Take the program above to check if the letter is uppercase or lowercase. In my humble opinion (which I know could be grossly wrong) it won't work. The if-condition condition worked because because ASCII has the values of "A" to "Z" in a sequence (decimal values: from 65 to 90).

Originally Posted by laserlight

Turn up your compiler warning level and attempt to compile some code like that. Then, if the compiler does not react as you expect, ask us why.

The warning for

Code:

cout << '++' << endl;

is: [Warning] multi-character character constant.

But it still runs and gives value of "11051". What's that?

By the way, what does it mean when a compiler gives warning(s)?

The error for

Code:

cout << ++ << endl;

is: expected primary-expression before '<<' token.

Why is so? Could you please tell?

Originally Posted by laserlight

Then you do something depending on what you are trying to do.

Hint: "what if" questions are nice for you to think out loud, but they require the reader to guess what your thoughts are if you don't actually think out loud your entire train of thoughts. Imagine going to a shop to buy a drink, and you ask the storekeeper "what if I bought this can of coke?" The storekeeper would have to figure out if he should say "then you have to pay me $1" or if he should say "then you would be missing out on this beer" (i.e., he has to figure out whether you are really asking how much it costs, or if you are asking his opinion on what drink to buy).

Okay, I understand your point. Now I'm trying to think loud. I want to use the character for the constant PI in a console program. I have its ASCII code which is 227. How do I do it.

Code:

Area = 2*PI*R;

Is it any clear or louder now?!

Originally Posted by laserlight

The term "sub-function" does not exist in standard C++, so you should explain what you understand by that term.

By sub-function I meant function within a function. "int main()" is the main function and its body contain the function "system()" as I was saying in my previous post.

Now please help me with the queries. Thank you for your help.

----------------

Hi Elysia

Originally Posted by Elysia

Please x 20 do NOT rely on ASCII. Don't mention it. Don't assume it is used. Don't even think about it.
The C++ standard does not guarantee what the "underlying character set" is. It could be ASCII, but it could also be something entirely different.
Furthermore, ASCII is an old american-only system. It needs to go away. Unicode is the new future as it is now.
So again, don't assume ASCII, and throw away your ASCII table.

Who/What is that "x 20"? Would you please tell me? Is it me?

If it is really me, then I won't mention it and throw it away just after using it a few times and along the way would try to learn Unicode. Happy!

Thank you all of you for guiding me on this stuff. You guys are really helpful.

Best wishes
Jackson

Originally Posted by jackson6612

If it doesn't really have English alphabet in contiguous manner, then how would it work? Take the program above to check if the letter is uppercase or lowercase. In my humble opinion (which I know could be grossly wrong) it won't work. The if-condition condition worked because because ASCII has the values of "A" to "Z" in a sequence (decimal values: from 65 to 90).

It works for ASCII, because the letters are contiguous. But all character sets are not guaranteed to be contiguous. Thus, the if statement may fail on some platforms.

The warning for

Code:

cout << '++' << endl;

is: [Warning] multi-character character constant.

But it still runs and gives value of "11051". What's that?

Single quotes detonate a single character. Yet, you are putting two characters inside the quotes. Hence, the compiler warns. The exact behavior is either implemented defined or undefined.

By the way, what does it mean when a compiler gives warning(s)?

It means you did something you shouldn't, or that you are doing something iffy. Basically, the compiler says "What's this? Is this really right?" and informs you that it's doubtful. Most of the cases, you did something bad.

The error for

Code:

cout << ++ << endl;

is: expected primary-expression before '<<' token.

Why is so? Could you please tell?

Because it's invalid syntax. ++ is an operator and must be applied to some variable. Strings always require double quotes.

Who/What is that "x 20"? Would you please tell me? Is it me?

x 20 was just meant to mean "repeat 20 times."

If it is really me, then I won't mention it and throw it away just after using it a few times and along the way would try to learn Unicode. Happy!

Good luck and try to keep a lot of sanity stored in reserve. Internationalization today is a pain.

Originally Posted by jackson6612

I want to use the character for the constant PI in a console program. I have its ASCII code which is 227. How do I do it.

It looks like you want to use the value of pi in your program, so you could approximate it with:

Code:

const double PI = 3.141593;

then use PI as in your statement.

Originally Posted by jackson6612

By sub-function I meant function within a function. "int main()" is the main function and its body contain the function "system()" as I was saying in my previous post.

Then no. Standard C++ does not allow for sub-functions. The use of system in main is a function call.

Originally Posted by jackson6612

If it is really me, then I won't mention it and throw it away just after using it a few times and along the way would try to learn Unicode.

Actually, ASCII is a subset of Unicode.

Originally Posted by Mozza314

Although I think you may run into problems with unsigned chars (char is signed, with values -128 to 127, so static_cast<char>(227) would overflow),

You definitely will not run into problems with unsigned chars with such a cast because 227 is within the guaranteed range of unsigned char. Whether char is signed or unsigned is implementation defined.

Originally Posted by laserlight

Actually, ASCII is a subset of Unicode.

Just a little addition to that:
ASCII is defined for 0-127 (ie 7 bits). The rest (128-255) are various extensions to ASCII that varies with code page. They are not the same in Unicode.
The first 127 characters (ie the standardized ASCII charset) is also the same in Unicode for backwards compatibility AFAIK.

It's probably more accurate to say that Unicode is a (terrible) rethink of text encoding.

It isn't a rethink of text encoding at all. It covers several text encodings; it is also much else besides.

The "Bidirectional Algorithm", for example, while only an annex, is still part of the standard.

For the most part it is unrelated to ASCII, and is not required to contain ASCII characters at all.

Yes; It absolutely does. That was part of the design goals of backwards compatibility with most existing protocols.

It just isn't compatible with "DOS-437" or "Windows-1252" that you probably know of as ASCII being a Windows guy.

Soma

Originally Posted by CommonTater

For the most part it is unrelated to ASCII, and is not required to contain ASCII characters at all.

From your own link: "The character sets of many existing international, national and corporate standards are incorporated within the Unicode Standard. For example, its first 256 characters are taken from the widely used Latin-1 character set." Consider that Latin-1 is one of those character sets based on ASCII.

Also: C0 Controls and Basic Latin (Range: 0000-007F)