On 12/2/22 4:18 PM, thebluepandabear wrote:
Hello (noob question),
I am reading a book about D by Ali, and he talks about the different
char types: char, wchar, and dchar. He says that char stores a UTF-8
code unit, wchar stores a UTF-16 code unit, and dchar stores a UTF-32
code unit, this makes sense.
He then goes on to say that:
"Contrary to some other programming languages, characters in D may
consist of
different numbers of bytes. For example, because 'Ğ' must be represented
by at
least 2 bytes in Unicode, it doesn't fit in a variable of type char. On
the other
hand, because dchar consists of 4 bytes, it can hold any Unicode
character."
It's his explanation as to why this code doesn't compile even though Ğ
is a UTF-8 code unit:
```D
char utf8 = 'Ğ';
```
But I don't really understand this? What does it mean that it 'must be
represented by at least 2 bytes'? If I do `char.sizeof` it's 2 bytes so
I am confused why it doesn't fit, I don't think it was explained well in
the book.
Any help would be appreciated.
a *code point* is a value out of the unicode standard. [Code
points](https://en.wikipedia.org/wiki/Code_point) represent glyphs,
combining marks, or other things (not sure of the full list) that reside
in the standard. When you want to figure out, "hmm... what value does
the emoji 👍 have?" It's a *code point*. This is a number from 0 to
0x10FFFF for Unicode. (BTW, it's 0x14ffd)
UTF-X are various *encodings* of unicode. UTF8 is an encoding of unicode
where 1 to 4 bytes (called *code units*) encode a single unicode *code
point*.
There are various encodings, and all can be decoded to the same list of
*code points*. The most direct form is UTF-32, where each *code point*
is also a *code unit*.
`char` is a UTF-8 code unit. `wchar` is a UTF-16 code unit, and `dchar`
is a UTF-32 code unit.
The reason why you can't encode a Ğ into a single `char` is because it's
code point is 0x11e, which does not fit into a single `char`. Therefore,
an encoding scheme is used to put it into 2 `char`.
Hope this helps.
-Steve
