Schar-format
Fixtype of formats of signed char objects.
This is a product type introduced by fty::defprod.
Fields
- signed — signed-format
- trap — booleanp
Values of the signed char type, like all the other values,
must be represented as one or more bytes [ISO:6.2.6.1/4].
Objects of the signed char type,
like all other signed integer objects,
must have no more value bits
than value bits of their unsigned counterpart
[ISO:6.2.6.2/2],
i.e. unsigned char objects in this case,
which consist of exactly one byte (see uchar-format):
therefore, signed char objects must take exactly one byte as well.
Since signed char objects must have one sign bit and no padding bits
[ISO:6.2.6.2/2],
they must have exactly \mathtt{CHAR\_BIT} - 1 value bits.
Since the values of the value bits of a signed integer type
must be equal to the value bits of the unsigned integer type counterpart
[ISO:6.2.6.2/2],
the value bits of signed char values are the low bits of the byte,
and the sign is the high bit.
While the byte/bit format of signed char is thus set,
the exact values represented by this byte/bit format depend on the signed format (when the sign bit is 1).
Furthermore, [ISO:6.2.6.2/2] identifies one specific bit pattern,
for each signed format,
as a possible trap representation:
it either is a trap representation or it is not.
These two choices
(i.e. the signed format,
and whether the specific pattern is a trap representation),
completely define the representation of signed char.
We formalize the format of signed char as consisting of
a specification of signed format
and a boolean flag saying whether the aforementioned pattern is a trap.
Subtopics
- Schar-format-fix
- Fixing function for schar-format structures.
- Schar-format-equiv
- Basic equivalence relation for schar-format structures.
- Make-schar-format
- Basic constructor macro for schar-format structures.
- Schar-format->signed
- Get the signed field from a schar-format.
- Change-schar-format
- Modifying constructor for schar-format structures.
- Schar-formatp
- Recognizer for schar-format structures.
- Schar-format->trap
- Get the trap field from a schar-format.
