1 /* S_LDEXP.C

     2  * 

     3  * Portions Copyright (c) 1993-2005 Nokia Corporation and/or its subsidiary(-ies).

     4  * All rights reserved.

     5  */

     6 

     7 

     8 /* @(#)s_ldexp.c 5.1 93/09/24 */

     9 /*

    10  * ====================================================

    11  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

    12  *

    13  * Developed at SunPro, a Sun Microsystems, Inc. business.

    14  * Permission to use, copy, modify, and distribute this

    15  * software is freely granted, provided that this notice 

    16  * is preserved.

    17  * ====================================================

    18  */

    19 

    20 /*

    21 FUNCTION

    22        <<ldexp>>, <<ldexpf>>---load exponent

    23 

    24 INDEX

    25 	ldexp

    26 INDEX

    27 	ldexpf

    28 

    29 ANSI_SYNOPSIS

    30        #include <math.h>

    31        double ldexp(double <[val]>, int <[exp]>);

    32        float ldexpf(float <[val]>, int <[exp]>);

    33 

    34 TRAD_SYNOPSIS

    35        #include <math.h>

    36 

    37        double ldexp(<[val]>, <[exp]>)

    38               double <[val]>;

    39               int <[exp]>;

    40 

    41        float ldexpf(<[val]>, <[exp]>)

    42               float <[val]>;

    43               int <[exp]>;

    44 

    45 

    46 DESCRIPTION

    47 <<ldexp>> calculates the value 

    48 @ifinfo

    49 <[val]> times 2 to the power <[exp]>.

    50 @end ifinfo

    51 @tex

    52 $val\times 2^{exp}$.

    53 @end tex

    54 <<ldexpf>> is identical, save that it takes and returns <<float>>

    55 rather than <<double>> values.

    56 

    57 RETURNS

    58 <<ldexp>> returns the calculated value.

    59 

    60 Underflow and overflow both set <<errno>> to <<ERANGE>>.

    61 On underflow, <<ldexp>> and <<ldexpf>> return 0.0.

    62 On overflow, <<ldexp>> returns plus or minus <<HUGE_VAL>>.

    63 

    64 PORTABILITY

    65 <<ldexp>> is ANSI, <<ldexpf>> is an extension.

    66               

    67 */   

    68 

    69 #include "FDLIBM.H"

    70 #include <errno.h>

    71 

    72 /**

    73 Get floating-point value from mantissa and exponent.

    74 Calculates the floating point value corresponding to 

    75 the given mantissa and exponent

    76 @return   Floating-point value equal to value * 2exp.

    77 @param x Floating point value representing mantissa 

    78 @param exp Integer exponent

    79 */	

    80 EXPORT_C double ldexp(double value, int exp) __SOFTFP

    81 {

    82 	if(!finite(value)||value==0.0) return value;

    83 	value = scalbn(value,exp);

    84 	if(!finite(value)||value==0.0) errno = ERANGE;

    85 	return value;

    86 }