<s>
In	O
the	O
C	B-Language
and	O
C++	B-Language
programming	I-Language
languages	I-Language
,	O
the	O
comma	B-Language
operator	I-Language
(	O
represented	O
by	O
the	O
token	O
,	O
)	O
is	O
a	O
binary	O
operator	O
that	O
evaluates	O
its	O
first	O
operand	O
and	O
discards	O
the	O
result	O
,	O
and	O
then	O
evaluates	O
the	O
second	O
operand	O
and	O
returns	O
this	O
value	O
(	O
and	O
type	O
)	O
;	O
there	O
is	O
a	O
sequence	B-Application
point	I-Application
between	O
these	O
evaluations	O
.	O
</s>
<s>
The	O
comma	B-Language
operator	I-Language
has	O
been	O
deprecated	B-General_Concept
in	O
subscripting	O
expressions	O
(	O
as	O
of	O
C++20	B-Language
)	O
;	O
to	O
reduce	O
confusion	O
,	O
and	O
open	O
up	O
the	O
future	O
possibility	O
of	O
repurposing	O
the	O
syntax	O
for	O
multidimensional	O
array	O
indexing	O
.	O
</s>
<s>
The	O
comma	B-Language
operator	I-Language
separates	O
expressions	O
(	O
which	O
have	O
value	O
)	O
in	O
a	O
way	O
analogous	O
to	O
how	O
the	O
semicolon	O
terminates	O
statements	O
,	O
and	O
sequences	O
of	O
expressions	O
are	O
enclosed	O
in	O
parentheses	O
analogously	O
to	O
how	O
sequences	O
of	O
statements	O
are	O
enclosed	O
in	O
braces	O
:	O
(	O
a	O
,	O
b	O
,	O
c	B-Language
)	O
is	O
a	O
sequence	O
of	O
expressions	O
,	O
separated	O
by	O
commas	O
,	O
which	O
evaluates	O
to	O
the	O
last	O
expression	O
c	B-Language
,	O
while	O
{	O
a	O
;	O
b	O
;	O
c	B-Language
;}	O
is	O
a	O
sequence	O
of	O
statements	O
,	O
and	O
does	O
not	O
evaluate	O
to	O
any	O
value	O
.	O
</s>
<s>
The	O
comma	B-Language
operator	I-Language
has	O
the	O
lowest	O
precedence	O
of	O
any	O
C	B-Language
operator	O
,	O
and	O
acts	O
as	O
a	O
sequence	B-Application
point	I-Application
.	O
</s>
<s>
In	O
a	O
combination	O
of	O
commas	O
and	O
semicolons	O
,	O
semicolons	O
have	O
lower	O
precedence	O
than	O
commas	O
,	O
as	O
semicolons	O
separate	O
statements	O
but	O
commas	O
occur	O
within	O
statements	O
,	O
which	O
accords	O
with	O
their	O
use	O
as	O
ordinary	O
punctuation	O
:	O
a	O
,	O
b	O
;	O
c	B-Language
,	O
d	O
is	O
grouped	O
as	O
(	O
a	O
,	O
b	O
)	O
;	O
(	O
c	B-Language
,	O
d	O
)	O
because	O
these	O
are	O
two	O
separate	O
statements	O
.	O
</s>
<s>
In	O
this	O
example	O
,	O
the	O
differing	O
behavior	O
between	O
the	O
second	O
and	O
third	O
lines	O
is	O
due	O
to	O
the	O
comma	B-Language
operator	I-Language
having	O
lower	O
precedence	O
than	O
assignment	O
.	O
</s>
<s>
The	O
comma	B-Language
operator	I-Language
has	O
relatively	O
limited	O
use	O
cases	O
.	O
</s>
<s>
Nevertheless	O
,	O
there	O
are	O
certain	O
circumstances	O
where	O
it	O
is	O
commonly	O
used	O
,	O
notably	O
in	O
for	B-Language
loops	I-Language
and	O
in	O
SFINAE	B-Language
.	O
</s>
<s>
For	O
embedded	O
systems	O
which	O
may	O
have	O
limited	O
debugging	O
capabilities	O
,	O
the	O
comma	B-Language
operator	I-Language
can	O
be	O
used	O
in	O
combination	O
with	O
a	O
macro	O
to	O
seamlessly	O
override	O
a	O
function	O
call	O
,	O
to	O
insert	O
code	O
just	O
before	O
the	O
function	O
call	O
.	O
</s>
<s>
The	O
most	O
common	O
use	O
is	O
to	O
allow	O
multiple	O
assignment	O
statements	O
without	O
using	O
a	O
block	O
statement	O
,	O
primarily	O
in	O
the	O
initialization	O
and	O
the	O
increment	O
expressions	O
of	O
a	O
for	B-Language
loop	I-Language
.	O
</s>
<s>
This	O
is	O
the	O
only	O
idiomatic	O
use	O
in	O
elementary	O
C	B-Language
programming	I-Language
.	O
</s>
<s>
This	O
is	O
used	O
in	O
Go	B-Application
in	O
its	O
analogous	O
for	B-Language
loop	I-Language
.	O
</s>
<s>
Outside	O
of	O
for	B-Language
loop	I-Language
initializers	O
(	O
which	O
have	O
a	O
special	O
use	O
of	O
semicolons	O
)	O
,	O
the	O
comma	O
might	O
be	O
used	O
instead	O
of	O
a	O
semicolon	O
,	O
particularly	O
when	O
the	O
statements	O
in	O
question	O
function	O
similarly	O
to	O
a	O
loop	O
increment	O
(	O
e.g.	O
</s>
<s>
assert	O
:	O
assert.c:6	O
:	O
test_assert	O
:	O
Assertion	O
`( 	O
"	O
i	O
is	O
too	O
big	O
!	O
</s>
<s>
A	O
similar	O
idiom	O
exists	O
in	O
Go	B-Application
,	O
where	O
the	O
syntax	O
of	O
the	O
if	O
statement	O
explicitly	O
allows	O
an	O
optional	O
statement	O
.	O
</s>
<s>
In	O
the	O
OCaml	B-Language
and	O
Ruby	B-Language
programming	I-Language
languages	I-Language
,	O
the	O
semicolon	O
(";	O
"	O
)	O
is	O
used	O
for	O
this	O
purpose	O
.	O
</s>
<s>
JavaScript	B-Language
and	O
Perl	B-Language
utilize	O
the	O
comma	B-Language
operator	I-Language
in	O
the	O
same	O
way	O
C/C	O
++	O
does	O
.	O
</s>
<s>
In	O
Java	B-Language
,	O
the	O
comma	O
is	O
a	O
separator	B-Algorithm
used	O
to	O
separate	O
elements	O
in	O
a	O
list	O
in	O
various	O
contexts	O
.	O
</s>
