C/C++ alternative preprocessing tokens

C++ has a set of alternative preprocessing tokens:
2.5/1
 and_eq &=
 and &&
 xor_eq ^=
 or ||
[..]


It turned out that C has them as well:
7.9

The header iso646.h defines the following eleven macros (on the left) that expand to
the corresponding tokens (on the right):

cat 4.6.3/include/iso646.h

#ifndef _ISO646_H
#define _ISO646_H

#ifndef __cplusplus
#define and     &&
#define and_eq  &=
#define bitand  &
#define bitor   |
#define compl   ~
#define not     !
#define not_eq  !=
#define or      ||
#define or_eq   |=
#define xor     ^
#define xor_eq  ^=
#endif

#endif