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%2Ffrexp.html | 79 +++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) create mode 100644 devdocs/c/numeric%2Fmath%2Ffrexp.html (limited to 'devdocs/c/numeric%2Fmath%2Ffrexp.html') diff --git a/devdocs/c/numeric%2Fmath%2Ffrexp.html b/devdocs/c/numeric%2Fmath%2Ffrexp.html new file mode 100644 index 00000000..60c85cff --- /dev/null +++ b/devdocs/c/numeric%2Fmath%2Ffrexp.html @@ -0,0 +1,79 @@ +

frexp, frexpf, frexpl

Defined in header <math.h> 
float       frexpf( float arg, int* exp );
+		 (1) (since C99) 
double      frexp( double arg, int* exp );
+		 (2) 
long double frexpl( long double arg, int* exp );
+		 (3) (since C99)
Defined in header <tgmath.h> 
#define frexp( arg, exp )
+		 (4) (since C99)
+1-3) Decomposes given floating point value x into a normalized fraction and an integral power of two.
+4) Type-generic macro: If arg has type long double, frexpl is called. Otherwise, if arg has integer type or the type double, frexp is called. Otherwise, frexpf is called, respectively.

Parameters

+ + +
arg - floating point value
exp - pointer to integer value to store the exponent to

Return value

If arg is zero, returns zero and stores zero in *exp.

+

Otherwise (if arg is not zero), if no errors occur, returns the value x in the range (-1;-0.5], [0.5; 1) and stores an integer value in *exp such that x×2(*exp)=arg.

+

If the value to be stored in *exp is outside the range of int, the behavior is unspecified.

+

If arg is not a floating-point number, the behavior is unspecified.

+

Error handling

This function is not subject to any errors specified in math_errhandling.

+

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

+

Notes

On a binary system (where FLT_RADIX is 2), frexp may be implemented as

+
{
+    *exp = (value == 0) ? 0 : (int)(1 + logb(value));
+    return scalbn(value, -(*exp));
+}

The function frexp, together with its dual, ldexp, can be used to manipulate the representation of a floating-point number without direct bit manipulations.

+

Example

#include <stdio.h>
+#include <math.h>
+#include <float.h>
+ 
+int main(void)
+{
+    double f = 123.45;
+    printf("Given the number %.2f or %a in hex,\n", f, f);
+ 
+    double f3;
+    double f2 = modf(f, &f3);
+    printf("modf() makes %.0f + %.2f\n", f3, f2);
+ 
+    int i;
+    f2 = frexp(f, &i);
+    printf("frexp() makes %f * 2^%d\n", f2, i);
+ 
+    i = ilogb(f);
+    printf("logb()/ilogb() make %f * %d^%d\n", f/scalbn(1.0, i), FLT_RADIX, i);
+}

Possible output:

+
Given the number 123.45 or 0x1.edccccccccccdp+6 in hex,
+modf() makes 123 + 0.45
+frexp() makes 0.964453 * 2^7
+logb()/ilogb() make 1.92891 * 2^6

References

See also

+ + + + +
+
(C99)(C99)
 multiplies a number by 2 raised to a power
(function)
+
(C99)(C99)(C99)
 extracts exponent of the given number
(function)
+
(C99)(C99)(C99)
 extracts exponent of the given number
(function)
+
(C99)(C99)
 breaks a number into integer and fractional parts
(function)
C++ documentation for frexp
+

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

+
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