source: altifloat/src/ur.h

forward(YREAL u1, YREAL u2, YREAL u3, YREAL u4, YREAL v1, YREAL v2, YREAL v3, YREAL v4, YREAL x1u, YREAL x2u, YREAL x3u, YREAL x4u, YREAL y1u, YREAL y2u, YREAL y3u, YREAL y4u, YREAL x1v, YREAL x2v, YREAL x3v, YREAL x4v, YREAL y1v, YREAL y2v, YREAL y3v, YREAL y4v,YREAL x, YREAL y)
{
        YS1=u1 + (u2-u1)*(x-x1u)+(u3-u1)*(y-y1u)+(u1-u2-u3+u4)*(x-x1u)*(y-y1u);
        YS2=v1 + (v2-v1)*(x-x1v)+(v3-v1)*(y-y1v)+(v1-v2-v3+v4)*(x-x1v)*(y-y1v);
        ur_dx=(u2-u1)+(u1-u2-u3+u4)*(y-y1u);
        ur_dy=(u3-u1)+(u1-u2-u3+u4)*(x-x1u);
        vr_dx=(v2-v1)+(v1-v2-v3+v4)*(y-y1v);
        vr_dy=(v3-v1)+(v1-v2-v3+v4)*(x-x1v);
        //printf("u1=%f ; u2=%f\n",u1,u2);
}


backward(YREAL u1, YREAL u2, YREAL u3, YREAL u4, YREAL v1, YREAL v2, YREAL v3, YREAL v4, YREAL x1u, YREAL x2u, YREAL x3u, YREAL x4u, YREAL y1u, YREAL y2u, YREAL y3u, YREAL y4u, YREAL x1v, YREAL x2v, YREAL x3v, YREAL x4v, YREAL y1v, YREAL y2v, YREAL y3v, YREAL y4v, YREAL x, YREAL y)

{
        YJ1I1 = 1 - (x-x1u) - (y-y1u) + (x-x1u)*(y-y1u);
        YJ2I5 = 1 - (x-x1v) - (y-y1v) + (x-x1v)*(y-y1v);
        YJ1I2 = (x-x1u)-(x-x1u)*(y-y1u);
        YJ2I6 = (x-x1v)-(x-x1v)*(y-y1v);
        YJ1I3 = (y-y1u)-(x-x1u)*(y-y1u);
        YJ2I7 = (y-y1v)-(x-x1v)*(y-y1v);
        YJ1I4 = (x-x1u)*(y-y1u);
        YJ2I8 = (x-x1v)*(y-y1v);
        YJ1I25=(u2-u1)+(u1-u2-u3+u4)*(y-y1u);
        YJ1I26=(u3-u1)+(u1-u2-u3+u4)*(x-x1u);
        YJ2I25=(v2-v1)+(v1-v2-v3+v4)*(y-y1v);
        YJ2I26=(v3-v1)+(v1-v2-v3+v4)*(x-x1v);
        }