ifcdlog.c

来自「开放源码的编译器open watcom 1.6.0版的源代码」· C语言 代码 · 共 50 行

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#include "variety.h"
#include "cplx.h"

_WMRTLINK dcomplex _IF_CDLOG( double rp, double ip )
//==================================================
{
// Return the logarithm (base e) of arg.
// ln(x + iy) = u + iv  =>  x + iy = exp(u) * cis(v)
// Thus x*x + y*y = exp(2u) or u = 0.5 ln(x*x + y*y)
// Also y/x = tan(v)  so  v = atan2(y,x)

    dcomplex    result;

    result.realpart = 0.5 * DLOG( rp*rp + ip*ip );
    result.imagpart = DATAN2( ip, rp );
    return( result );
}