sl@0: // Copyright (c) 1995-2009 Nokia Corporation and/or its subsidiary(-ies).
sl@0: // All rights reserved.
sl@0: // This component and the accompanying materials are made available
sl@0: // under the terms of the License "Eclipse Public License v1.0"
sl@0: // which accompanies this distribution, and is available
sl@0: // at the URL "http://www.eclipse.org/legal/epl-v10.html".
sl@0: //
sl@0: // Initial Contributors:
sl@0: // Nokia Corporation - initial contribution.
sl@0: //
sl@0: // Contributors:
sl@0: //
sl@0: // Description:
sl@0: // e32\euser\maths\um_tan.cpp
sl@0: // Tangent.
sl@0: // 
sl@0: //
sl@0: 
sl@0: #include "um_std.h"
sl@0: 
sl@0: #if defined(__USE_VFP_MATH) && !defined(__CPU_HAS_VFP)
sl@0: #error	__USE_VFP_MATH was defined but not __CPU_HAS_VFP - impossible combination, check variant.mmh 
sl@0: #endif
sl@0: 
sl@0: 
sl@0: #ifndef __USE_VFP_MATH
sl@0: 
sl@0: LOCAL_D const TUint32 TanCoeffs[] =
sl@0: 	{
sl@0: 	0x2168C235,0xC90FDAA2,0x7FFF0000,	// polynomial approximation to tan((pi/2)*x)
sl@0: 	0x2DF4707D,0xA55DE731,0x7FFF0000,	// for |x|<=0.25
sl@0: 	0xA9A1A71A,0xA335E33B,0x7FFF0000,
sl@0: 	0x0BB9E431,0xA2FFFCDD,0x7FFF0000,
sl@0: 	0x3E523A39,0xA2FA3863,0x7FFF0000,
sl@0: 	0x8A35C401,0xA2F9D38B,0x7FFF0000,
sl@0: 	0x91269411,0xA2F16003,0x7FFF0000,
sl@0: 	0xDA32CC78,0xA3A93B13,0x7FFF0000,
sl@0: 	0x4FB88317,0x9A146197,0x7FFF0000,
sl@0: 	0x0D787ECE,0xE131DEE5,0x7FFF0000
sl@0: 	};
sl@0: 
sl@0: LOCAL_D const TUint32 Onedata[] = {0x00000000,0x80000000,0x7FFF0000};		// 1.0
sl@0: LOCAL_D const TUint32 Halfdata[] = {0x00000000,0x80000000,0x7FFE0000};		// 0.5
sl@0: LOCAL_D const TUint32 PiBy2Invdata[] = {0x4E44152A,0xA2F9836E,0x7FFE0000};	// 2/pi
sl@0: 
sl@0: 
sl@0: 
sl@0: 
sl@0: EXPORT_C TInt Math::Tan(TReal& aTrg, const TReal& aSrc)
sl@0: /**
sl@0: Calculates the tangent of a number.
sl@0: 
sl@0: @param aTrg A reference containing the result.
sl@0: @param aSrc The argument of the tan function in radians. 
sl@0: 
sl@0: @return KErrNone if successful, otherwise another of
sl@0:         the system-wide error codes. 
sl@0: */
sl@0: 	{
sl@0: 	// Calculate tan(aSrc) and write result to aTrg.
sl@0: 	// Algorithm:
sl@0: 	//		Let x=aSrc/(pi/2). Throw away integer part, but if integer part odd
sl@0: 	//			then replace final result y with -1/y
sl@0: 	//			( use identities tan(x+n*pi)=tan(x), tan(x+pi/2)=-1/tan(x) )
sl@0: 	//		Replace x with fractional part after division.
sl@0: 	//		If x>=0.5, replace x with 1-x and replace result y with 1/y
sl@0: 	//			( use identity tan(pi/2-x)=1/tan(x) )
sl@0: 	//		If x>=0.25, replace x with 0.5-x and replace result y with (1-y)/(1+y)
sl@0: 	//			( use identity tan(pi/4-x)=(1-tan(x))/(1+tan(x)) )
sl@0: 	//		Use polynomial approximation to calculate tan(pi*x/2) for |x|<=0.25
sl@0: 
sl@0: 	const TRealX& One = *(const TRealX*)Onedata;
sl@0: 	const TRealX& Half = *(const TRealX*)Halfdata;
sl@0: 	const TRealX& PiBy2Inv = *(const TRealX*)PiBy2Invdata;
sl@0: 
sl@0: 	TRealX x;
sl@0: 	TInt r=x.Set(aSrc);
sl@0: 	if (r==KErrNone)
sl@0: 		{
sl@0: 		TInt8 sign=x.iSign;
sl@0: 		x.iSign=0;
sl@0: 		x*=PiBy2Inv;
sl@0: 		TInt n=(TInt)x;
sl@0: 		if (n<KMaxTInt && n>KMinTInt)
sl@0: 			{
sl@0: 			TInt flags=(n&1)<<1;
sl@0: 			x-=TRealX(n);
sl@0: 			if (x.iExp>=0x7FFE)
sl@0: 				{
sl@0: 				x=One-x;
sl@0: 				flags^=2;
sl@0: 				}
sl@0: 			if (x.iExp>=0x7FFD)
sl@0: 				{
sl@0: 				x=Half-x;
sl@0: 				flags^=1;
sl@0: 				}
sl@0: 			TRealX y;
sl@0: 			PolyX(y,x*x,9,(const TRealX*)TanCoeffs);
sl@0: 			y*=x;
sl@0: 			if (flags==3)
sl@0: 				y=(One+y)/(One-y);
sl@0: 			else if (flags==2)
sl@0: 				y=One/y;
sl@0: 			else if (flags==1)
sl@0: 				y=(One-y)/(One+y);
sl@0: 			y.iSign=TInt8(sign ^ (n&1));
sl@0: 			return y.GetTReal(aTrg);
sl@0: 			}
sl@0: 		}
sl@0: 	SetNaN(aTrg);
sl@0: 	return KErrArgument;
sl@0: 	}
sl@0: 
sl@0: #else // __USE_VFP_MATH
sl@0: 
sl@0: // definitions come from RVCT math library
sl@0: extern "C" TReal tan(TReal);
sl@0: 
sl@0: EXPORT_C TInt Math::Tan(TReal& aTrg, const TReal& aSrc)
sl@0: 	{
sl@0: 	if (aSrc<KMaxTInt && aSrc>KMinTInt)
sl@0: 		{
sl@0: 		aTrg = tan(aSrc);
sl@0: 		if (Math::IsFinite(aTrg))
sl@0: 			return KErrNone;
sl@0: 		}
sl@0: 	SetNaN(aTrg);
sl@0: 	return KErrArgument;
sl@0: 	}
sl@0: 
sl@0: #endif