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Annotation of researchv10no/libplot/lib4014/parabola.c, revision 1.1

1.1     ! root        1: #include <math.h>
        !             2: #include <stdio.h>
        !             3: #include "tek.h"
        !             4: parabola(x0, y0, x1, y1, xb, yb) 
        !             5: double x0, y0, x1, y1, xb, yb; 
        !             6: {
        !             7:        register double x, y, t;
        !             8:        double  c0x, c0y, c1x, c1y;
        !             9:        double  dt, d2, d1;
        !            10:        d1 = sqrt((xb - x0) * (xb - x0) + (yb - y0) * (yb - y0));
        !            11:        d2 = sqrt((xb - x1) * (xb - x1) + (yb - y1) * (yb - y1));
        !            12:        if (d1 <= e1->quantum || d2 <= e1->quantum) { 
        !            13:                line(x0, y0, x1, y1); 
        !            14:                return(0); 
        !            15:        }
        !            16:        c0x = x0 + x1 - 2. * xb; 
        !            17:        c1x = 2. * (xb - x0);
        !            18:        c0y = y0 + y1 - 2. * yb; 
        !            19:        c1y = 2. * (yb - y0);
        !            20:        move(x0, y0);
        !            21:        dt = e1->quantum / d1;
        !            22:        if(e1->grade != 0.)
        !            23:                dt /= e1->grade;
        !            24:        for (t = dt; t < 0.5; t += dt) {
        !            25:                x = (c0x * t + c1x) * t + x0;
        !            26:                y = (c0y * t + c1y) * t + y0;
        !            27:                vec(x, y);
        !            28:        }
        !            29:        dt = e1->quantum / d2;
        !            30:        if(e1->grade != 0.)
        !            31:                dt /= e1->grade;
        !            32:        for (; t < 1.0; t += dt) {
        !            33:                x = (c0x * t + c1x) * t + x0;
        !            34:                y = (c0y * t + c1y) * t + y0;
        !            35:                vec(x, y);
        !            36:        }
        !            37:        vec(x1, y1);
        !            38: }

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