Why C11 define character constant recursively?

Question

The character constants are defined in c11 as:
Syntax
character-constant:
' c-char-sequence '
L' c-char-sequence '
u' c-char-sequence '
U' c-char-sequence '
c-char-sequence:
c-char
c-char-sequence c-char
c-char:
any member of the source character set except the single-quote ', backslash \, or new-line character
escape-sequence

It is defined recursively, so inside the single-quotes, there are one or more c-chars, like 'abc'.
However as I know, a character constant contains only one c-char, like 'a', doesn't it?

Characters are UTF-8 as far as I know. It can support characters beyond what ASCII can. See here stackoverflow.com/questions/10229156/… — Dustin Nieffenegger
The Macintosh File System used four bytes constants for file types and file application creator, like 'TEXT' for a text file, 'APPL' for an application. File name extensions were rarely used (mostly used for programming and web publishing). — curiousguy

Cubbi Cubbi · Accepted Answer · 2017-04-19T03:17:04

as I know, a character constant contains only one c-char, like 'a', doesn't it?

no, 'abcd' is also a character constant. Its value is technically implementation-defined, but everywhere I've looked it was formed out of the values of the chars, in big-endian order (in that case, 0x61626364)

The C side of cppreference has a discussion of various character constants

Why C11 define character constant recursively?

1 Answers