Example of contour functions in Turbo C++ 

typedef struct PT_XY
{
double dblXX, dblYY;
} PT_XY;

#define MAX_PTX (int)30

PT_XY funcY(double dblXX, PT_XY ptx[MAX_PTX]);
double fFac(double dblX);
double fFac2(double dblX);
double fWF1(double dblX, double dblN);
double fWF2(double dblX, double dblN);



FILE *fCalc;
PT_XY xy, ptxy[MAX_PTX], pti[MAX_PTX];
double dblY, dblX, dblX2, dblXX, dblDOld;
int i,ii,dxchk, mp;
char szT[300];
double dblDX[201], dblDY[201],dblTot, dblN, dblDT;
BOOL bDELTAYGROOT;

if ((fCalc = fopen("hallo.lxt", "wb")) != NULL)
{
// delta X step init...
dxchk = (int)111;
// te verdelen punten...
dblN = (double)1111.0;
// opvatting van delta x verdeling...
bDELTAYGROOT = (BOOL)TRUE;
// bDELTAYGROOT = (BOOL)FALSE;

for (mp=0;mp<MAX_PTX;mp++)
{
// pti[mp].dblXX = (double)0.5 * M_PI;
// pti[mp].dblYY = (double)0.5 * M_PI;

// pti[mp].dblXX = (double)0.0;
// pti[mp].dblYY = (double)0.0;

pti[mp].dblXX = (double)1.0;
pti[mp].dblYY = (double)1.0;

ptxy[mp] = pti[mp];
}
dblTot = (double)0.0;
dblDOld = (double)1.0;
for (i=0;i<dxchk;i++)
{
dblX = (double)i/(double)dxchk;

xy = funcY(dblX, ptxy);
for (mp=MAX_PTX-1;mp>0;mp--)
{
ptxy[mp] = ptxy[mp-1];
}
ptxy[0] = xy;

dblDX[i] = xy.dblXX;
dblDY[i] = xy.dblYY;
dblX = (double)(i+(int)1)/(double)dxchk;

xy = funcY(dblX, ptxy);
// ptxy = xy;

dblDX[i] = fabs(dblDX[i] - xy.dblXX);
dblDY[i] = fabs(dblDY[i] - xy.dblYY);

if (bDELTAYGROOT)
{
// AFGELEIDE grote delta y -> x veel punten
if (dblDX[i] != (double)0.0)
{
dblDX[i] = dblDY[i] / dblDX[i];
}
else
{
dblDX[i] = (double)1.0;
}
}
else
{
// AFGELEIDE kleine delta y -> x veel punten
if (dblDY[i] != (double)0.0)
{
dblDX[i] = dblDX[i] / dblDY[i];
}
else
{
dblDX[i] = (double)1.0;
}
}

/*
// hoek verandering relativeren...
// ??????
if (i>(int)0)
{
dblDT = dblDX[i];
dblDX[i] = dblDX[i] / dblDOld;
dblDOld = dblDT;
}
else
{
dblDOld = dblDX[(int)0];
dblDX[(int)0] = (double)1.0;
}
*/


dblTot = dblTot + dblDX[i];
}
for (i=0;i<dxchk;i++)
{
if (dblTot != (double)0.0)
{
dblDX[i] = dblDX[i] / dblTot;
}
dblDX[i] = dblDX[i] * dblN;
dblDX[i] = ceil(dblDX[i]);
}
for (mp=0;mp<MAX_PTX;mp++)
{
ptxy[mp] = pti[mp];
}
for (i=0;i<dxchk;i++)
{
dblXX = (double)i/(double)dxchk;
dblX2 = (double)(i+(int)1)/(double)dxchk;
for (ii=0;ii<dblDX[i];ii++)
{
dblX = dblXX + ((dblX2 - dblXX) / dblDX[i]) * (double)ii;

xy = funcY(dblX, ptxy);
for (mp=MAX_PTX-1;mp>0;mp--)
{
ptxy[mp] = ptxy[mp-1];
}
ptxy[0] = xy;

sprintf(szT, "%.10lf, %.10lf,\n", xy.dblXX, xy.dblYY);
fputs(szT, fCalc);
}
}

dblX = (double)i/(double)dxchk;

xy = funcY(dblX, ptxy);
for (mp=MAX_PTX-1;mp>0;mp--)
{
ptxy[mp] = ptxy[mp-1];
}
ptxy[0] = xy;

sprintf(szT, "%.10lf, %.10lf,\n", xy.dblXX, xy.dblYY);
fputs(szT, fCalc);


strcpy(szT, "\n\n\n");
fputs(szT, fCalc);

fclose(fCalc);


/*
for (i=-10;i<=10;i++)
{
dblX = (double)i;
dblY = pow(dblX,(double)3) + pow(dblX, (double)2) + dblX + pow
(fabs(dblX),(double)0.5);
sprintf(szT, "%.10lf, %.10lf,\n", dblX, dblY);
fputs(szT, fCalc);
}
strcpy(szT, "\n\n\n");
fputs(szT, fCalc);

fclose(fCalc);
*/
}

LineFuncData.hDC = ps.hdc;
SetTextAlign( ps.hdc, TA_BOTTOM );
LineDDA( 0, 0, 0,
rect.bottom / 2, lpLineFunc, (LPSTR) &LineFuncData );
EndPaint( hWnd, &ps );
FreeProcInstance( lpLineFunc );
}

PT_XY funcY(double dblXX, PT_XY ptx[MAX_PTX])
{
double dblX2, dblYY, dblXH, dblYY2;
PT_XY xy2, xyh;
int mp,mps, mpg;

dblXH = dblXX;

dblXX = dblXX * (double)1.0 * M_PI;
xy2.dblXX = dblXX * dblXX * cos(dblXX);
xy2.dblYY = dblXX * sin(dblXX);

// dblXX = dblXX * (double)0.5 * M_PI + (double)0.25 * M_PI;
// xy2.dblXX = dblXX * dblXX;
// xy2.dblYY = pow(sin(dblXX), (double)3.0);

// dblXX = dblXX * (double)0.5 * M_PI;
// xy2.dblXX = sin(dblXX);
// xy2.dblYY = pow(cos(dblXX), (double)3.0);

// dblXX = dblXX * M_PI;
// xy2.dblXX = pow(dblXX, (double)2.0);
// xy2.dblYY = sin(dblXX);

// dblXX = dblXX * (double)4.0;
// xy2.dblXX = sqrt(dblXX);
// xy2.dblXX = pow(dblXX, (double)0.2);
// dblXX = dblXX - (double)2.0;
// xy2.dblYY = pow(dblXX, (double)5.0);

// xy2.dblXX = dblXX;
// dblXX = dblXX * (double)0.5 * M_PI;
// xy2.dblYY = cos(dblXX);
// if (dblXX >= (double)0.25 * M_PI)
// {
// dblXX = dblXX - (double)0.25 * M_PI;
// xy2.dblYY = xy2.dblYY * pow(cos(dblXX), (double)2.0);
// }

// xy2.dblXX = (ptx[1].dblXX + ptx[6].dblXX) * 0.1 + (ptx[1].dblYY +
ptx[6].dblYY) * 0.25;
// xy2.dblYY = (ptx[2].dblYY + ptx[3].dblYY) * 0.25 + (ptx[2].dblXX
+ ptx[3].dblXX) * 0.1;

// xy2.dblXX = sin(ptx[2].dblXX + cos(ptx[5].dblYY));
// xy2.dblYY = cos(0.5 * ptx[3].dblXX * ptx[5].dblXX);

// xy2.dblXX = 3+fabs(sin(fabs(log(ptx[0].dblXX + ptx[5].dblYY))));
// xy2.dblYY = 3+fabs(cos(fabs(log(ptx[0].dblXX + ptx[10].dblYY))));

// xy2.dblXX = fabs(log10(ptx[0].dblXX + ptx[1].dblYY));
// xy2.dblYY = fabs(sqrt(ptx[0].dblXX + ptx[2].dblYY));

// xy2.dblXX = dblXX;
// xy2.dblYY = sqrt(1-dblXX*dblXX);

// xy2.dblXX = sqrt(ptx[4].dblXX + ptx[3].dblYY);
// xy2.dblYY = ptx[2].dblXX + ptx[5].dblYY;
// xy2.dblXX /= 100000000;
// xy2.dblYY /= 100000000;

// mps=20;
// dblX2 = (double)0.0;
// dblYY = (double)0.0;
// for (mp=0;mp<mps;mp++)
// {
// dblX2 = dblX2 + ptx[mp].dblXX + ptx[mp].dblYY;
// dblYY = dblYY + ptx[mp].dblYY;
// }
// xy2.dblXX = dblX2 / (double)mps;
// xy2.dblYY = dblYY / (double)mps + sin(xy2.dblXX);

// mps=20;
// dblX2 = (double)0.0;
// dblYY = (double)0.0;
// dblX2 = dblX2 + ptx[0].dblXX + ptx[0].dblYY;
// dblYY = dblYY + ptx[0].dblYY;
// dblX2 = dblX2 + 19*(ptx[1].dblXX + ptx[1].dblYY);
// dblYY = dblYY + 19*ptx[1].dblYY;
// xy2.dblXX = dblX2 / (double)mps;
// xy2.dblYY = dblYY / (double)mps + cos(xy2.dblXX);

// mps=21;
// mpg=0;
// dblX2 = (double)0.0;
// dblYY = (double)0.0;
// for (mp=0;mp<mps;mp+=5)
// {
// dblX2 = dblX2 + ptx[mp].dblXX + ptx[mp].dblYY;
// dblYY = dblYY + ptx[mp].dblYY;
// mpg++;
// }
// xy2.dblXX = dblX2 / (double)mpg;
// xy2.dblYY = dblYY / (double)mpg + cos(xy2.dblXX);


// mps=20;
// dblX2 = (double)0.0;
// dblYY = (double)0.0;
// for (mp=0;mp<mps;mp++)
// {
// dblX2 = dblX2 + ptx[mp].dblXX + ptx[mp].dblYY;
// dblYY = dblYY + ptx[mp].dblYY;
// }
// xy2.dblXX = dblX2 / (double)mps;
// xy2.dblYY = dblYY / (double)mps + cos(xy2.dblXX);


// dblXX = dblXX * (double)2.0 * M_PI;
// xy2.dblXX = sin(sin(sin(ptx.dblXX + ptx.dblYY)));
// xy2.dblYY = sin(sin(cos(ptx.dblXX + ptx.dblYY)));

// xy2.dblXX = dblXX;
// xy2.dblYY = sqrt(1-dblXX*dblXX);
// xy2.dblYY = pow((double)10, dblXX);
// xy2.dblYY /= (double)2.0;

// dblXX = dblXX * (double)4.0;
// xy2.dblXX = dblXX;
// xy2.dblYY = sqrt(dblXX);
// xy2.dblYY += (double)0.125 * dblXX * dblXX;
// xy2.dblYY /= (double)2.0;

// dblXX = dblXX * (double)2.0 * M_PI;
// xy2.dblXX = dblXX;
// xy2.dblYY = sin(dblXX);

// xy2.dblXX = log(pow(10, 2 * dblXX + 1));
// xy2.dblYY = sqrt((double)1.0 - dblXX * dblXX);

// xy2.dblXX = log10(pow(10, 2 * dblXX + 1));
// xy2.dblYY = sqrt((double)1.0 - dblXX * dblXX);

// dblXX = dblXX * (double)2.0 * M_PI;
// xy2.dblXX = (dblXH + (double)1.0) * cos(dblXX);
// xy2.dblYY = (dblXH + (double)1.0) * sin(dblXX);
// xy2.dblXX = xy2.dblXX * sin((double)4.0 * dblXX);
// xy2.dblYY = xy2.dblYY * cos((double)4.0 * dblXX);

// dblXX = dblXX * (double)3.0 * M_PI;
// xy2.dblXX = (dblXH + (double)1.0) * cos(dblXX);
// xy2.dblYY = (dblXH + (double)1.0) * sin(dblXX);
// xy2.dblXX = xy2.dblXX * sin((double)4.0 * dblXX);
// xy2.dblYY = xy2.dblYY * cos((double)4.0 * dblXX);

// dblXX = dblXX * (double)2.0 * M_PI;
// xy2.dblXX = (pow(exp(1), dblXH) - (double)1.0) * cos(dblXX);
// xy2.dblYY = (pow(exp(1), dblXH) - (double)1.0) * sin(dblXX);
// xy2.dblXX = xy2.dblXX * sin((double)4.0 * dblXX);
// xy2.dblYY = xy2.dblYY * cos((double)4.0 * dblXX);

// xy2.dblXX = dblXX;
// xy2.dblYY = sqrt(pow((double)1.0, (double)4.0) - pow(dblXX,
(double)4.0));

// dblXX = dblXX * (double)0.5 * M_PI;
// xy2.dblXX = dblXX;
// xy2.dblYY = sin(dblXX * (double)0.5 * M_PI);

// dblXX = dblXX * (double)2.0 * M_PI;
// xy2.dblXX = sin(sin(dblXX) + (double)2.0);
// xy2.dblYY = sin(cos(dblXX) + (double)2.0);

// dblXX = dblXX * (double)2.0 * M_PI;
// xy2.dblXX = pow((double)3.0, sin(dblXX) + (double)2.0);
// xy2.dblYY = pow((double)3.0, cos(dblXX) + (double)2.0);

// dblXX = dblXX * (double)2.0 * M_PI;
// xy2.dblXX = sqrt(sin(dblXX) + (double)2.0);
// xy2.dblYY = sqrt(cos(dblXX) + (double)2.0);

// dblXX = dblXX * (double)2.0 * M_PI;
// xy2.dblXX = log(sin(dblXX) + (double)2.0);
// xy2.dblYY = log(cos(dblXX) + (double)2.0);

// dblXX = dblXX * (double)10.0;
// xy2.dblXX = tan(dblXX);
// xy2.dblYY = dblXX / (sqrt(dblXX) + (double)1.0);

// dblXX = dblXX * (double)10.0;
// xy2.dblXX = sqrt(dblXX);
// xy2.dblYY = pow(dblXX, (double)2.0);


// dblXX = dblXX * (double)9.0 * M_PI;

// dblXH = dblXH * (double)0.5 * M_PI - (double)0.25 * M_PI;
// dblXH = tan(dblXH) + (double)1.0;
// dblXH = tan(dblXH) + (double)1.0;

// dblXH = dblXH * (double)2.0 - (double)1.0;
// dblYY2 = dblXH + (double)2.0;
// dblYY2 = dblYY2 * dblYY2;
// dblXH = pow(dblXH, (double)3.0) + pow((double)1.0, (double)3.0) /
dblYY2;

// dblXH = dblXH * (double)2.0 - (double)1.0;
// dblXH = atan(dblXH) + (double)0.25 * M_PI;

// dblXH = pow((double)3.0, (double)3.0 * dblXH + (double)1.0) -
(double)3.0;

// xy2.dblXX = dblXH * cos(dblXX);
// xy2.dblYY = dblXH * sin(dblXX);


// dblXX = dblXX * (double)6.0 * M_PI;
// xy2.dblXX = dblXX * cos(dblXX);
// xy2.dblYY = dblXX * sin(dblXX);

// dblXX = dblXX * (double)3.0 * M_PI;
// dblXH = pow((double)10.0, (dblXH) * (double)2.0 + (double)1.0);
// xy2.dblXX = (3-log10(1010-dblXH)) * cos(dblXX);
// xy2.dblYY = (3-log10(1010-dblXH)) * sin(dblXX);

// dblXX = dblXX * (double)4.0 * M_PI;
// dblXH = pow((double)10.0, dblXH * (double)6.0 + (double)1.0);
// xy2.dblXX = (log10(dblXH) - (double)1.0) * cos(dblXX);
// xy2.dblYY = (log10(dblXH) - (double)1.0) * sin(dblXX);

// dblXX = dblXX * (double)4.0 * M_PI;
// dblXH = pow((double)10.0, dblXH * (double)2.0);
// xy2.dblXX = (log10(dblXH) - (double)1.0) * cos(dblXX);
// xy2.dblYY = (log10(dblXH) - (double)1.0) * sin(dblXX);

// dblXX = dblXX * (double)4.0 * M_PI;
// dblXH = dblXH * (double)90.0 + (double)10.0;
// xy2.dblXX = (log10(dblXH) - (double)1.0) * cos(dblXX);
// xy2.dblYY = (log10(dblXH) - (double)1.0) * sin(dblXX);

// xy2.dblXX = cosh(ptx.dblYY) - cosh(ptx.dblXX);
// xy2.dblYY = sinh(ptx.dblYY) - sinh(ptx.dblXX);
// xy2.dblXX = xy2.dblXX / (double)1000.0;
// xy2.dblYY = xy2.dblYY / (double)1000.0;

// xy2.dblXX = sin(ptx.dblYY) - sin(ptx.dblXX);
// xy2.dblYY = cos(ptx.dblYY) - cos(ptx.dblXX);
// xy2.dblXX = xy2.dblXX / (double)1000.0;
// xy2.dblYY = xy2.dblYY / (double)1000.0;

// xy2.dblXX = sin(ptx.dblYY) + sin(ptx.dblYY);
// xy2.dblYY = cos(ptx.dblXX) + cos(ptx.dblXX);
// xy2.dblXX = xy2.dblXX / (double)1000.0;
// xy2.dblYY = xy2.dblYY / (double)1000.0;

// xy2.dblXX = (ptx.dblXX + 6) / (ptx.dblYY + 3);
// xy2.dblYY = cos(ptx.dblXX) - cos(ptx.dblYY);
// xy2.dblXX = xy2.dblXX / (double)1000.0;
// xy2.dblYY = xy2.dblYY / (double)1000.0;

// xy2.dblXX = (ptx.dblXX + 3) / (ptx.dblYY + 1);
// xy2.dblYY = ptx.dblXX - ptx.dblYY;
// xy2.dblXX = xy2.dblXX / (double)1000.0;
// xy2.dblYY = xy2.dblYY / (double)1000.0;

// xy2.dblXX = dblXX;
// xy2.dblYY = sqrt((double)1.0 - dblXX * dblXX);

// xy2.dblXX = ptx.dblXX + ptx.dblYY;
// xy2.dblYY = cos(ptx.dblXX) + cos(ptx.dblYY);

// dblXX = dblXX * (double)10.0;
// xy2.dblXX = ptx.dblXX + (double)1.0;
// xy2.dblXX = dblXX;
// dblYY2 = fFac2(xy2.dblXX);
// xy2.dblYY = fFac(xy2.dblXX);
// xy2.dblYY = xy2.dblYY + dblYY2;

// dblXX = dblXX * (double)90.0 + (double)10.0;
// xy2.dblXX = log10(dblXX);
// xy2.dblYY = pow(xy2.dblXX, xy2.dblXX);

// dblXX = dblXX * (double)4.0 * M_PI;
// dblXX = dblXX - (double)2.0 * M_PI;
// xy2.dblXX = dblXX * dblXX * dblXX;
// xy2.dblYY = cos(dblXX) * cos(dblXX) * cos(dblXX);

// ptx.dblXX = ptx.dblXX * sin(ptx.dblYY);
// ptx.dblYY = ptx.dblYY * sin(ptx.dblXX);
// xy2.dblXX = log(ptx.dblXX + (double)3.0) * log10(ptx.dblYY +
(double)10.0);
// xy2.dblYY = log10(ptx.dblXX + (double)10.0) / log(ptx.dblYY +
(double)3.0) + cos(ptx.dblXX) + cos(ptx.dblYY);
// xy2.dblYY = log(ptx.dblXX + (double)3.0) / log10(ptx.dblYY +
(double)10.0);

// dblXX = dblXX * (double)99.0 + (double)1.0;
// xy2.dblXX = log(dblXX) * log10(dblXX) * sin(dblXX * M_PI /
(double)25.0);
// xy2.dblYY = log10(dblXX);

// dblXX = dblXX * (double)10.0;
// xy2.dblXX = dblXX * dblXX;
// xy2.dblXX = xy2.dblXX * (double)0.8 + (double)10.0;
// dblXX = dblXX - (double)5.0;
// xy2.dblYY = (double)-1.0 * (dblXX * dblXX);
// xy2.dblYY = xy2.dblYY * ((double)15.0/(double)25.0) - (double)
10.0;

// dblYY2 = (double)80.0;
// ptx.dblXX = ptx.dblXX * M_PI;
// ptx.dblYY = ptx.dblYY * M_PI;
// xy2.dblXX = fWF1(ptx.dblXX, dblYY2) + fWF2(ptx.dblYY, dblYY2);
// xy2.dblYY = fWF2(ptx.dblXX, dblYY2) + fWF1(ptx.dblYY, dblYY2);

// xy2.dblXX = ptx.dblXX + cos(ptx.dblYY + ptx.dblXX);
// xy2.dblYY = ptx.dblYY + ptx.dblXX;

// xy2.dblXX = ptx.dblYY * ptx.dblYY - ptx.dblYY * ptx.dblXX;
// xy2.dblYY = ptx.dblYY * ((double)1.0 - ptx.dblYY);

// xy2.dblXX = cos(ptx.dblYY * ptx.dblYY * ptx.dblXX) + (double)
100.0 * atan(ptx.dblYY + ptx.dblXX);
// xy2.dblYY = sin(ptx.dblXX * ptx.dblYY + (double)3.5 * ptx.dblXX)
+ (double)100.0 * atan(ptx.dblYY);
// xy2.dblXX = xy2.dblXX / (double)1.0;
// xy2.dblYY = xy2.dblYY / (double)1.0;

// xy2.dblXX = ptx.dblXX + ptx.dblYY;
// xy2.dblYY = ptx.dblYY - (double)1.5 * cos(ptx.dblXX + ptx.dblYY);

// chshrt1
// xy2.dblXX = atan(ptx.dblYY) * ptx.dblXX;
// xy2.dblYY = sin(ptx.dblXX) * ptx.dblYY;

// xy2.dblXX = 0.75 * (fWF1(ptx.dblXX, 20.0) * fFac(ptx.dblYY)) *
fWF1(ptx.dblYY,30.0);
// xy2.dblYY = 1.25 * (fWF1(ptx.dblYY, 20.0) * fFac(ptx.dblXX)) *
fWF1(ptx.dblXX,30.0);
// xy2.dblXX = xy2.dblXX / (double)1000000.0;
// xy2.dblYY = xy2.dblYY / (double)1000000.0;

// xy2.dblXX = dblXX;
// xy2.dblYY = ((double)4.0 / (double)3.0) * ptx.dblYY;

return(xy2);
}

double fFac2(double dblX)
{
double dblRet;

dblRet = (double)1.0;
if (dblX > (double)0.0)
{
while (dblX > (double)0.0)
{
dblRet = dblRet * dblX;
dblX = dblX - (double)2.0;
}
}

return(dblRet);
}

double fFac(double dblX)
{
double dblRet;

dblRet = (double)1.0;
if (dblX > (double)0.0)
{
while (dblX > (double)0.0)
{
dblRet = dblRet * dblX;
dblX = dblX - (double)1.0;
}
}

return(dblRet);
}

double fWF1(double dblX, double dblN)
{
double dblRet, dblNN, dblTel, dblSGN;

dblRet = (double)0.0;
dblNN = (double)1.0;
dblTel = (double)1.0;
dblSGN = (double)1.0;
while (dblTel <= dblN)
{
dblRet = dblRet + dblSGN * pow(cos(dblX), dblNN) / fFac(dblNN);
dblSGN = dblSGN * (double)-1.0;
dblNN = dblNN + (double)2.0;
dblTel = dblTel + (double)1.0;
}

return(dblRet);
}

double fWF2(double dblX, double dblN)
{
double dblRet, dblNN, dblTel, dblSGN;

dblRet = (double)0.0;
dblNN = (double)2.0;
dblTel = (double)1.0;
dblSGN = (double)1.0;
while (dblTel <= dblN)
{
dblRet = dblRet + dblSGN * pow(cos(dblX), dblNN) / fFac(dblNN);
dblSGN = dblSGN * (double)-1.0;
dblNN = dblNN + (double)2.0;
dblTel = dblTel + (double)1.0;
}

return(dblRet);
}

/*
double fWF1(double dblX, double dblN)
{
double dblRet, dblNN, dblTel, dblSGN;

dblRet = (double)0.0;
dblNN = (double)1.0;
dblTel = (double)1.0;
dblSGN = (double)1.0;
while (dblTel <= dblN)
{
dblRet = dblRet + dblSGN * sin(dblX*dblNN) / (dblNN * dblNN);
dblSGN = dblSGN * (double)-1.0;
dblNN = dblNN + (double)2.0;
dblTel = dblTel + (double)1.0;
}

return(dblRet);
}
*/