some relationen for floating point values are implemented as macros
add missing iseqsig and try to motivate the rationale with an example
Signed-off-by: Radisson <Radisson97@xxxxxx>
---
man3/isgreater.3 | 44 +++++++++++++++++++++++++++++++++++++++++---
1 file changed, 41 insertions(+), 3 deletions(-)
diff --git a/man3/isgreater.3 b/man3/isgreater.3
index 7c1f2a7c5..10767c393 100644
--- a/man3/isgreater.3
+++ b/man3/isgreater.3
@@ -9,8 +9,8 @@
.\"
.TH ISGREATER 3 2021-03-22 "" "Linux Programmer's Manual"
.SH NAME
-isgreater, isgreaterequal, isless, islessequal, islessgreater,
-isunordered \- floating-point relational tests without exception for NaN
+isgreater, isgreaterequal, isless, islessequal, islessgreater, iseqsig,
+isunordered \- floating-point comparison functions
.SH SYNOPSIS
.nf
.B #include <math.h>
@@ -20,6 +20,7 @@ isunordered \- floating-point relational tests without exception for NaN
.BI "int isless(" x ", " y );
.BI "int islessequal(" x ", " y );
.BI "int islessgreater(" x ", " y );
+.BI "int iseqsig(" x ", " y );
.BI "int isunordered(" x ", " y );
.fi
.PP
@@ -97,6 +98,10 @@ is NaN.
.BR isunordered ()
determines whether its arguments are unordered, that is, whether
at least one of the arguments is a NaN.
+.TP
+.BR iseqsig ()
+determines \fI(x)\ ==\ (y) \fP. It differs from the comparison by
+rasing an exeption if either argument is a NaN.
.SH RETURN VALUE
The macros other than
.BR isunordered ()
@@ -109,6 +114,9 @@ returns 1 if
or
.I y
is NaN and 0 otherwise.
+.PP
+.BR iseqsig ()
+sets errno to EDOM if either argument is a NaN.
.SH ERRORS
No errors occur.
.SH ATTRIBUTES
@@ -127,12 +135,42 @@ T{
.BR isless (),
.BR islessequal (),
.BR islessgreater (),
-.BR isunordered ()
+.BR isunordered (),
+.BR iseqsig ()
T} Thread safety MT-Safe
.TE
.hy
.ad
.sp 1
+.SH EXAMPLE
+The example demonstates the difference between the equal operator
+and
+.BR iseqsig ().
+The return value is the same but errno is different.
+.EX
+.nf
+/*
+ * gcc -lm iseqsig.c -o iseqsig
+*/
+#include <stdio.h>
+#include <math.h>
+#include <string.h>
+#include <errno.h>
+
+int main()
+{
+ double x=0.0/0.0;
+ double y=0.0;
+
+ printf("%d ",x==y);
+ puts(strerror(errno));
+ printf("%d ",iseqsig(x,y));
+ puts(strerror(errno));
+ return 0;
+}
+.fi
+.EE
+
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, C99.
.SH NOTES
--
2.26.2
