.TH LIBJ2_J2I_SUB_J2I 3 LIBJ2
.SH NAME
libj2_j2i_sub_j2i \- Calculate difference

.SH SYNOPSIS
.nf
#include <libj2.h>

void \fBlibj2_j2i_sub_j2i\fP(struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP);
void \fBlibj2_j2i_sub_j2i_to_j2i\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);
void \fBlibj2_j2i_sub_ji\fP(struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP);
void \fBlibj2_j2i_sub_ji_to_j2i\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP, struct libj2_j2i *\fIr\fP);
void \fBlibj2_ji_sub_j2i_to_j2i\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);
void \fBlibj2_ji_sub_ji_to_j2i\fP(intmax_t \fIa\fP, intmax_t \fIb\fP, struct libj2_j2i *\fIr\fP);

int \fBlibj2_j2i_sub_j2i_overflow\fP(struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP);
int \fBlibj2_j2i_sub_j2i_to_j2i_overflow\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);
int \fBlibj2_j2i_sub_ji_overflow\fP(struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP);
int \fBlibj2_j2i_sub_ji_to_j2i_overflow\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP, struct libj2_j2i *\fIr\fP);
int \fBlibj2_ji_sub_j2i_to_j2i_overflow\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);

int \fBlibj2_j2i_sub_j2i_overflow_p\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP);
int \fBlibj2_j2i_sub_ji_overflow_p\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP);
int \fBlibj2_ji_sub_j2i_overflow_p\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP);

void \fBlibj2_j2i_sub_j2i_carry\fP(struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP, int *\fIc\fP);
void \fBlibj2_j2i_sub_j2i_to_j2i_carry\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP, int *\fIc\fP);

void \fBlibj2_j2i_rsub_j2i\fP(struct libj2_j2i *\fIb\fP, const struct libj2_j2i *\fIa\fP);
void \fBlibj2_j2i_rsub_ji\fP(struct libj2_j2i *\fIb\fP, intmax_t \fIa\fP);

int \fBlibj2_j2i_rsub_j2i_overflow\fP(struct libj2_j2i *\fIb\fP, const struct libj2_j2i *\fIa\fP);
int \fBlibj2_j2i_rsub_ji_overflow\fP(struct libj2_j2i *\fIb\fP, intmax_t \fIa\fP);

int \fBlibj2_j2i_rsub_j2i_overflow_p\fP(const struct libj2_j2i *\fIb\fP, const struct libj2_j2i *\fIa\fP);
int \fBlibj2_j2i_rsub_ji_overflow_p\fP(const struct libj2_j2i *\fIb\fP, intmax_t \fIa\fP);

void \fBlibj2_j2i_rsub_j2i_carry\fP(struct libj2_j2i *\fIb\fP, const struct libj2_j2i *\fIa\fP, int *\fIc\fP);

void \fBlibj2_j2i_sat_sub_j2i\fP(struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP);
void \fBlibj2_j2i_sat_sub_j2i_to_j2i\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);
void \fBlibj2_j2i_sat_sub_ji\fP(struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP);
void \fBlibj2_j2i_sat_sub_ji_to_j2i\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP, struct libj2_j2i *\fIr\fP);
void \fBlibj2_ji_sat_sub_j2i_to_j2i\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);

void \fBlibj2_j2i_sat_rsub_j2i\fP(struct libj2_j2i *\fIb\fP, const struct libj2_j2i *\fIa\fP);
void \fBlibj2_j2i_sat_rsub_ji\fP(struct libj2_j2i *\fIb\fP, intmax_t \fIa\fP);
.fi
.PP
Link with
.IR -lj2 .

.SH DESCRIPTION
The above listed functions calculate the
difference of the values of
.I a
(the minuend)
and
.I b
(the subtrahend).
The functions with the parameter
.I r
store the result in
.IR r ,
the other functions store the result in
.IR a ,
except the functions
.BR libj2_j2i_sub_j2i_overflow_p (),
.BR libj2_j2i_sub_ji_overflow_p (),
.BR libj2_ji_sub_j2i_overflow_p (),
.BR libj2_j2i_rsub_j2i_overflow_p (),
and
.BR libj2_j2i_rsub_ji_overflow_p ()
only predict overflow, and do not calculate
the difference, and therefore does store it
anywhere; and except the functions
.BR libj2_j2i_rsub_j2i (),
.BR libj2_j2i_rsub_ji (),
.BR libj2_j2i_rsub_j2i_overflow (),
.BR libj2_j2i_rsub_ji_overflow (),
.BR libj2_j2i_sat_rsub_j2i (),
and
.BR libj2_j2i_sat_rsub_ji ()
store the result in
.IR b .
.PP
The value-returning functions (that is, those
with word
.B overflow
in their name), detect arithmetic overflow.
.PP
The
.BR libj2_j2i_sub_j2i_carry (),
.BR libj2_j2i_sub_j2i_to_j2i_carry (),
and
.BR libj2_j2i_rsub_j2i_carry ()
functions add
.IR *c ,
which must be +1, -1, or 0,
to the result, and sets
.I *c
to +1 on positive overflow,
-1 on negative overflow, and 0 otherwise.
.PP
The result is truncated to the least significant
bits, as many as can be stored, in case of overflow;
that is, modular arithmetics is used. However, the
.BR sat_sub -
and
.BR sat_rsub -functions
use saturated arithmetics, meaning that the result
will be the maximum representable value on positive
overflow and the minimum representable value on
negative overflow.
.PP
The arguments are assumed to be
.RI non- NULL .

.SH RETURN VALUE
For functions with a return value, the functions
return +1 if the result is positive but too large
to be represented, -1 if the result is negative
but too large, and 0 otherwise.

.SH ERRORS
The above listed functions cannot fail.

.SH HISTORY
The
.BR libj2_j2i_sub_j2i (),
.BR libj2_j2i_sub_j2i_to_j2i (),
.BR libj2_j2i_sub_ji (),
.BR libj2_j2i_sub_ji_to_j2i (),
.BR libj2_ji_sub_j2i_to_j2i (),
.BR libj2_ji_sub_ji_to_j2i (),
.BR libj2_j2i_sub_j2i_overflow (),
.BR libj2_j2i_sub_j2i_to_j2i_overflow (),
.BR libj2_j2i_sub_ji_overflow (),
.BR libj2_j2i_sub_ji_to_j2i_overflow (),
.BR libj2_ji_sub_j2i_to_j2i_overflow (),
.BR libj2_j2i_sub_j2i_overflow_p (),
.BR libj2_j2i_sub_ji_overflow_p (),
.BR libj2_ji_sub_j2i_overflow_p (),
.BR libj2_j2i_rsub_j2i (),
.BR libj2_j2i_rsub_ji (),
.BR libj2_j2i_rsub_j2i_overflow (),
.BR libj2_j2i_rsub_ji_overflow (),
.BR libj2_j2i_rsub_j2i_overflow_p (),
.BR libj2_j2i_rsub_ji_overflow_p (),
.BR libj2_j2i_sat_sub_j2i (),
.BR libj2_j2i_sat_sub_j2i_to_j2i (),
.BR libj2_j2i_sat_sub_ji (),
.BR libj2_j2i_sat_sub_ji_to_j2i (),
.BR libj2_ji_sat_sub_j2i_to_j2i (),
.BR libj2_j2i_sat_rsub_j2i (),
and
.BR libj2_j2i_sat_rsub_ji ()
functions were added in version 1.1 of
.BR libj2 .
.PP
The
.BR libj2_j2i_sub_j2i_carry (),
.BR libj2_j2i_sub_j2i_to_j2i_carry (),
and
.BR libj2_j2i_rsub_j2i_carry ()
functions were added in version 1.2 of
.BR libj2 .

.SH SEE ALSO
.BR libj2 (7),
.BR libj2_j2u_sub_j2u (3),
.BR libj2_j2u_abs_diff_j2u (3),
.BR libj2_j2i_add_j2i (3),
.BR libj2_j2i_mul_j2i (3),
.BR libj2_j2i_divmod_j2i (3)