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[AROS.git] / workbench / libs / mathieeesingtrans / ieeespexp.c
blob86b63b13f64065d79de9d3b6a44f6faa6caedc25
1 /*
2 Copyright © 1995-2003, The AROS Development Team. All rights reserved.
3 $Id$
4 */
6 #include "mathieeesingtrans_intern.h"
8 /*****************************************************************************
10 NAME */
12 AROS_LH1(float, IEEESPExp,
14 /* SYNOPSIS */
15 AROS_LHA(float, y, D0),
17 /* LOCATION */
18 struct Library *, MathIeeeSingTransBase, 13, MathIeeeSingTrans)
20 /* FUNCTION
21 Calculate e^x
23 INPUTS
25 RESULT
27 BUGS
28 IEEE single precision number
30 flags:
31 zero : result is zero
32 negative : 0
33 overflow : the result was out of range for the IEEE single precision
34 format
36 INTERNALS
37 e^(>= 89): return 0x7f800000;
38 e^(2^(<=-24)): return one;
40 *****************************************************************************/
42 AROS_LIBFUNC_INIT
44 const LONG ExpTable[] =
46 0x6da12cc2, /* e^64 */
47 0x568fa1fe, /* e^32 */
48 0x4b07975e, /* e^16 */
49 0x453a4f53, /* e^8 */
50 0x425a6481, /* e^4 */
51 0x40ec7325, /* e^2 */
52 0x402df854, /* e^1 */
53 0x3fd3094c, /* e^(1/2) */
54 0x3fa45af2, /* e^(1/4) */
55 0x3f910b02, /* e^(1/8) */
56 0x3f88415b, /* e^(1/16) */
57 0x3f84102b, /* e^(1/32) */
58 0x3f820405, /* e^(1/64) */
59 0x3f810101, /* e^(1/128) */
60 0x3f808040, /* e^(1/256) */
61 0x3f804010, /* e^(1/512) */
62 0x3f802004, /* e^(1/1024) */
63 0x3f801001, /* e^(1/2048) */
64 0x3f800800, /* e^(1/4096) */
65 0x3f800400, /* e^(1/8192) */
66 0x3f800200, /* e^(1/16384) */
67 0x3f800100, /* e^(1/32768) */
68 0x3f800080, /* e^(1/65536) */
69 0x3f800040, /* e^(1/131072) */
70 0x3f800020, /* e^(1/262144) */
71 0x3f800010, /* e^(1/524288) */
72 0x3f800008, /* e^(1/1048576) */
73 0x3f800004, /* e^(1/2097152) */
74 0x3f800002, /* e^(1/4194304) */
75 0x3f800001, /* e^(1/8388608) */
77 ULONG Res, i;
78 LONG Mantisse;
79 char Exponent;
81 Exponent = ((y & IEEESPExponent_Mask) >> 23) -0x7f;
83 /* e^0 = 1, e^(2^(<=-24)) = 1 */
84 if ( 0 == y || Exponent <= -24 ) return one;
86 /* e^(>= 89) = overflow) */
87 if (Exponent > 6)
89 SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
90 return IEEESP_Pinfty;
93 i = 6 - Exponent;
95 Mantisse = (y & IEEESPMantisse_Mask) << 9;
96 Res = ExpTable[i++];
98 while ( 0 != Mantisse && i <= 29 )
100 /* is the highest bit set? */
101 if ( Mantisse < 0 )
103 Res = IEEESPMul(Res, ExpTable[i]);
104 if (0 == Res)
106 SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
107 return Res;
109 if (IEEESP_Pinfty == Res)
111 SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
112 return Res;
115 i++;
116 Mantisse <<= 1;
119 if ( y < 0) return IEEESPDiv(one, Res);
121 return Res;
123 AROS_LIBFUNC_EXIT