| .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
| .\" |
| .\" %%%LICENSE_START(VERBATIM) |
| .\" Permission is granted to make and distribute verbatim copies of this |
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| .\" |
| .\" Permission is granted to copy and distribute modified versions of this |
| .\" manual under the conditions for verbatim copying, provided that the |
| .\" entire resulting derived work is distributed under the terms of a |
| .\" permission notice identical to this one. |
| .\" |
| .\" Since the Linux kernel and libraries are constantly changing, this |
| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
| .\" responsibility for errors or omissions, or for damages resulting from |
| .\" the use of the information contained herein. The author(s) may not |
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| .\" Formatted or processed versions of this manual, if unaccompanied by |
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| .\" %%%LICENSE_END |
| .\" |
| .\" References consulted: |
| .\" Linux libc source code |
| .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) |
| .\" 386BSD man pages |
| .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) |
| .\" Modified 2002-07-27 by Walter Harms |
| .\" (walter.harms@informatik.uni-oldenburg.de) |
| .\" |
| .TH FREXP 3 2021-03-22 "" "Linux Programmer's Manual" |
| .SH NAME |
| frexp, frexpf, frexpl \- convert floating-point number to fractional |
| and integral components |
| .SH SYNOPSIS |
| .nf |
| .B #include <math.h> |
| .PP |
| .BI "double frexp(double " x ", int *" exp ); |
| .BI "float frexpf(float " x ", int *" exp ); |
| .BI "long double frexpl(long double " x ", int *" exp ); |
| .fi |
| .PP |
| Link with \fI\-lm\fP. |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR frexpf (), |
| .BR frexpl (): |
| .nf |
| _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L |
| || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
| || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE |
| .fi |
| .SH DESCRIPTION |
| These functions are used to split the number |
| .I x |
| into a |
| normalized fraction and an exponent which is stored in |
| .IR exp . |
| .SH RETURN VALUE |
| These functions return the normalized fraction. |
| If the argument |
| .I x |
| is not zero, |
| the normalized fraction is |
| .I x |
| times a power of two, |
| and its absolute value is always in the range 1/2 (inclusive) to |
| 1 (exclusive), that is, [0.5,1). |
| .PP |
| If |
| .I x |
| is zero, then the normalized fraction is |
| zero and zero is stored in |
| .IR exp . |
| .PP |
| If |
| .I x |
| is a NaN, |
| a NaN is returned, and the value of |
| .I *exp |
| is unspecified. |
| .PP |
| If |
| .I x |
| is positive infinity (negative infinity), |
| positive infinity (negative infinity) is returned, and the value of |
| .I *exp |
| is unspecified. |
| .SH ERRORS |
| No errors occur. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR frexp (), |
| .BR frexpf (), |
| .BR frexpl () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| C99, POSIX.1-2001, POSIX.1-2008. |
| .PP |
| The variant returning |
| .I double |
| also conforms to |
| SVr4, 4.3BSD, C89. |
| .SH EXAMPLES |
| The program below produces results such as the following: |
| .PP |
| .in +4n |
| .EX |
| .RB "$" " ./a.out 2560" |
| frexp(2560, &e) = 0.625: 0.625 * 2\(ha12 = 2560 |
| .RB "$" " ./a.out \-4" |
| frexp(\-4, &e) = \-0.5: \-0.5 * 2\(ha3 = \-4 |
| .EE |
| .in |
| .SS Program source |
| \& |
| .EX |
| #include <math.h> |
| #include <float.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| double x, r; |
| int exp; |
| |
| x = strtod(argv[1], NULL); |
| r = frexp(x, &exp); |
| |
| printf("frexp(%g, &e) = %g: %g * %d\(ha%d = %g\en", |
| x, r, r, FLT_RADIX, exp, x); |
| exit(EXIT_SUCCESS); |
| } |
| .EE |
| .SH SEE ALSO |
| .BR ldexp (3), |
| .BR modf (3) |