1 // Copyright (c) 1995-2009 Nokia Corporation and/or its subsidiary(-ies).

     2 // All rights reserved.

     3 // This component and the accompanying materials are made available

     4 // under the terms of the License "Symbian Foundation License v1.0"

     5 // which accompanies this distribution, and is available

     6 // at the URL "http://www.symbianfoundation.org/legal/sfl-v10.html".

     7 //

     8 // Initial Contributors:

     9 // Nokia Corporation - initial contribution.

    10 //

    11 // Contributors:

    12 //

    13 // Description:

    14 // e32\euser\maths\um_tan.cpp

    15 // Tangent.

    16 // 

    17 //

    18 

    19 #include "um_std.h"

    20 

    21 #if defined(__USE_VFP_MATH) && !defined(__CPU_HAS_VFP)

    22 #error	__USE_VFP_MATH was defined but not __CPU_HAS_VFP - impossible combination, check variant.mmh 

    23 #endif

    24 

    25 

    26 #ifndef __USE_VFP_MATH

    27 

    28 LOCAL_D const TUint32 TanCoeffs[] =

    29 	{

    30 	0x2168C235,0xC90FDAA2,0x7FFF0000,	// polynomial approximation to tan((pi/2)*x)

    31 	0x2DF4707D,0xA55DE731,0x7FFF0000,	// for |x|<=0.25

    32 	0xA9A1A71A,0xA335E33B,0x7FFF0000,

    33 	0x0BB9E431,0xA2FFFCDD,0x7FFF0000,

    34 	0x3E523A39,0xA2FA3863,0x7FFF0000,

    35 	0x8A35C401,0xA2F9D38B,0x7FFF0000,

    36 	0x91269411,0xA2F16003,0x7FFF0000,

    37 	0xDA32CC78,0xA3A93B13,0x7FFF0000,

    38 	0x4FB88317,0x9A146197,0x7FFF0000,

    39 	0x0D787ECE,0xE131DEE5,0x7FFF0000

    40 	};

    41 

    42 LOCAL_D const TUint32 Onedata[] = {0x00000000,0x80000000,0x7FFF0000};		// 1.0

    43 LOCAL_D const TUint32 Halfdata[] = {0x00000000,0x80000000,0x7FFE0000};		// 0.5

    44 LOCAL_D const TUint32 PiBy2Invdata[] = {0x4E44152A,0xA2F9836E,0x7FFE0000};	// 2/pi

    45 

    46 

    47 

    48 

    49 EXPORT_C TInt Math::Tan(TReal& aTrg, const TReal& aSrc)

    50 /**

    51 Calculates the tangent of a number.

    52 

    53 @param aTrg A reference containing the result.

    54 @param aSrc The argument of the tan function in radians. 

    55 

    56 @return KErrNone if successful, otherwise another of

    57         the system-wide error codes. 

    58 */

    59 	{

    60 	// Calculate tan(aSrc) and write result to aTrg.

    61 	// Algorithm:

    62 	//		Let x=aSrc/(pi/2). Throw away integer part, but if integer part odd

    63 	//			then replace final result y with -1/y

    64 	//			( use identities tan(x+n*pi)=tan(x), tan(x+pi/2)=-1/tan(x) )

    65 	//		Replace x with fractional part after division.

    66 	//		If x>=0.5, replace x with 1-x and replace result y with 1/y

    67 	//			( use identity tan(pi/2-x)=1/tan(x) )

    68 	//		If x>=0.25, replace x with 0.5-x and replace result y with (1-y)/(1+y)

    69 	//			( use identity tan(pi/4-x)=(1-tan(x))/(1+tan(x)) )

    70 	//		Use polynomial approximation to calculate tan(pi*x/2) for |x|<=0.25

    71 

    72 	const TRealX& One = *(const TRealX*)Onedata;

    73 	const TRealX& Half = *(const TRealX*)Halfdata;

    74 	const TRealX& PiBy2Inv = *(const TRealX*)PiBy2Invdata;

    75 

    76 	TRealX x;

    77 	TInt r=x.Set(aSrc);

    78 	if (r==KErrNone)

    79 		{

    80 		TInt8 sign=x.iSign;

    81 		x.iSign=0;

    82 		x*=PiBy2Inv;

    83 		TInt n=(TInt)x;

    84 		if (n<KMaxTInt && n>KMinTInt)

    85 			{

    86 			TInt flags=(n&1)<<1;

    87 			x-=TRealX(n);

    88 			if (x.iExp>=0x7FFE)

    89 				{

    90 				x=One-x;

    91 				flags^=2;

    92 				}

    93 			if (x.iExp>=0x7FFD)

    94 				{

    95 				x=Half-x;

    96 				flags^=1;

    97 				}

    98 			TRealX y;

    99 			PolyX(y,x*x,9,(const TRealX*)TanCoeffs);

   100 			y*=x;

   101 			if (flags==3)

   102 				y=(One+y)/(One-y);

   103 			else if (flags==2)

   104 				y=One/y;

   105 			else if (flags==1)

   106 				y=(One-y)/(One+y);

   107 			y.iSign=TInt8(sign ^ (n&1));

   108 			return y.GetTReal(aTrg);

   109 			}

   110 		}

   111 	SetNaN(aTrg);

   112 	return KErrArgument;

   113 	}

   114 

   115 #else // __USE_VFP_MATH

   116 

   117 // definitions come from RVCT math library

   118 extern "C" TReal tan(TReal);

   119 

   120 EXPORT_C TInt Math::Tan(TReal& aTrg, const TReal& aSrc)

   121 	{

   122 	if (aSrc<KMaxTInt && aSrc>KMinTInt)

   123 		{

   124 		aTrg = tan(aSrc);

   125 		if (Math::IsFinite(aTrg))

   126 			return KErrNone;

   127 		}

   128 	SetNaN(aTrg);

   129 	return KErrArgument;

   130 	}

   131 

   132 #endif