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.Dd July 8, 2018
.Dt Q_SIGNED 3
.Os
.Sh NAME
.Nm Q_SIGNED ,
.Nm Q_LTZ ,
.Nm Q_PRECEQ ,
.Nm Q_QLTQ ,
.Nm Q_QLEQ ,
.Nm Q_QGTQ ,
.Nm Q_QGEQ ,
.Nm Q_QEQ ,
.Nm Q_QNEQ ,
.Nm Q_OFLOW ,
.Nm Q_RELPREC
.Nd fixed-point math comparison and logic functions
.Sh SYNOPSIS
.In sys/qmath.h
.Ft bool
.Fn Q_SIGNED "NTYPE n"
.Ft bool
.Fn Q_LTZ "NTYPE n"
.Ft bool
.Fn Q_PRECEQ "QTYPE a" "QTYPE b"
.Ft bool
.Fn Q_QLTQ "QTYPE a" "QTYPE b"
.Ft bool
.Fn Q_QLEQ "QTYPE a" "QTYPE b"
.Ft bool
.Fn Q_QGTQ "QTYPE a" "QTYPE b"
.Ft bool
.Fn Q_QGEQ "QTYPE a" "QTYPE b"
.Ft bool
.Fn Q_QEQ "QTYPE a" "QTYPE b"
.Ft bool
.Fn Q_QNEQ "QTYPE a" "QTYPE b"
.Ft bool
.Fn Q_OFLOW "QTYPE q" "ITYPE iv"
.Ft int
.Fn Q_RELPREC "QTYPE a" "QTYPE b"
.Sh DESCRIPTION
.Fn Q_SIGNED
returns
.Ft true
if the numeric data type passed in as
.Fa n
is signed, or
.Ft false
otherwise.
.Pp
.Fn Q_LTZ
returns
.Ft true
if the numeric value
passed in as
.Fa n
is negative
.Pq requires types which use the MSB as the sign bit ,
or
.Ft false
otherwise.
.Pp
.Fn Q_PRECEQ
returns
.Ft true
if the number of
.Fa a
and
.Fa b
fractional bits is the same,
.Ft false
otherwise.
.Pp
The
.Fn Q_QLTQ ,
.Fn Q_QLEQ ,
.Fn Q_QGTQ ,
.Fn Q_QGEQ ,
.Fn Q_QEQ
and
.Fn Q_QNEQ
functions compare two Q numbers, returning
.Ft true
if
.Fa a
is less than, less than or equal to, greater than, greater than or equal to,
equal to, or not equal to
.Fa b
respectively, or
.Ft false
otherwise.
The integral and fractional values are used to perform the comparison, without
explicit concern for the underlying number of integer versus fractional bits.
.Pp
.Fn Q_OFLOW
returns
.Ft true
if integer value
.Fa iv
cannot be stored in
.Fa q
without truncation, or false otherwise.
.Pp
.Fn Q_RELPREC
returns the relative precision of
.Fa a
versus
.Fa b .
In terms of
.Em Qm.n
notation, this function returns the difference between the
.Em n
values of
.Fa a
and
.Fa b .
For example, a return value of +4 means that
.Fa a
has an additional 4 bits of fractional precision compared to
.Fa b .
.Pp
All of those functions operate on
the following data types:
.Vt s8q_t ,
.Vt u8q_t ,
.Vt s16q_t ,
.Vt u16q_t ,
.Vt s32q_t ,
.Vt u32q_t ,
.Vt s64q_t ,
and
.Vt u64q_t ,
which are referred to generically as
.Fa QTYPE .
The
.Fa ITYPE
refers to the
.Xr stdint 7
integer types.
.Fa NTYPE
is used to refer to any numeric type and is therefore a superset of
.Fa QTYPE
and
.Fa ITYPE .
.Pp
For more details, see
.Xr qmath 3 .
.Sh RETURN VALUES
The
.Fn Q_SIGNED ,
.Fn Q_LTZ ,
.Fn Q_PRECEQ ,
.Fn Q_QLTQ ,
.Fn Q_QLEQ ,
.Fn Q_QGTQ ,
.Fn Q_QGEQ ,
.Fn Q_QEQ ,
.Fn Q_QNEQ
and
.Fn Q_OFLOW
functions return expressions that evaluate to boolean
.Vt true
or
.Vt false .
.Pp
.Fn Q_RELPREC
returns the relative precision difference as a signed integer.
.Sh SEE ALSO
.Xr errno 2 ,
.Xr qmath 3 ,
.Xr stdint 7
.Sh HISTORY
The
.Xr qmath 3
functions first appeared in
.Fx 13.0 .
.Sh AUTHORS
.An -nosplit
The
.Xr qmath 3
functions and this manual page were written by
.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org
and sponsored by Netflix, Inc.