From 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 Mon Sep 17 00:00:00 2001 From: Craig Jennings Date: Sun, 7 Apr 2024 13:41:34 -0500 Subject: new repository --- devdocs/c/numeric%2Fmath%2Fisnan.html | 51 +++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) create mode 100644 devdocs/c/numeric%2Fmath%2Fisnan.html (limited to 'devdocs/c/numeric%2Fmath%2Fisnan.html') diff --git a/devdocs/c/numeric%2Fmath%2Fisnan.html b/devdocs/c/numeric%2Fmath%2Fisnan.html new file mode 100644 index 00000000..f9b432de --- /dev/null +++ b/devdocs/c/numeric%2Fmath%2Fisnan.html @@ -0,0 +1,51 @@ +

isnan

Defined in header <math.h> 
#define isnan(arg) /* implementation defined */
+		 (since C99)

Determines if the given floating point number arg is a not-a-number (NaN) value. The macro returns an integral value.

+

FLT_EVAL_METHOD is ignored: even if the argument is evaluated with more range and precision than its type, it is first converted to its semantic type, and the classification is based on that (this matters if the evaluation type supports NaNs, while the semantic type does not).

+

Parameters

+ +
arg - floating point value

Return value

Nonzero integral value if arg is a NaN, ​0​ otherwise.

+

Notes

There are many different NaN values with different sign bits and payloads, see nan.

+

NaN values never compare equal to themselves or to other NaN values. Copying a NaN may change its bit pattern.

+

Another way to test if a floating-point value is NaN is to compare it with itself: bool is_nan(double x) { return x != x; }

+

Example

#include <stdio.h>
+#include <math.h>
+#include <float.h>
+ 
+int main(void)
+{
+    printf("isnan(NAN)         = %d\n", isnan(NAN));
+    printf("isnan(INFINITY)    = %d\n", isnan(INFINITY));
+    printf("isnan(0.0)         = %d\n", isnan(0.0));
+    printf("isnan(DBL_MIN/2.0) = %d\n", isnan(DBL_MIN/2.0));
+    printf("isnan(0.0 / 0.0)   = %d\n", isnan(0.0/0.0));
+    printf("isnan(Inf - Inf)   = %d\n", isnan(INFINITY - INFINITY));
+}

Possible output:

+
isnan(NAN)         = 1
+isnan(INFINITY)    = 0
+isnan(0.0)         = 0
+isnan(DBL_MIN/2.0) = 0
+isnan(0.0 / 0.0)   = 1
+isnan(Inf - Inf)   = 1

References

See also

+ + + + + + +
+
(C99)(C99)(C99)
 returns a NaN (not-a-number)
(function)
+
(C99)
 classifies the given floating-point value
(function macro)
+
(C99)
 checks if the given number has finite value
(function macro)
+
(C99)
 checks if the given number is infinite
(function macro)
+
(C99)
 checks if the given number is normal
(function macro)
+
(C99)
 checks if two floating-point values are unordered
(function macro)
C++ documentation for isnan
+

+ © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
+ https://en.cppreference.com/w/c/numeric/math/isnan +

+
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