how should i check for multiple line intersection if I return boolean status i can check but how to reshuffle the end point each time

if (x < (min(x1, x2) - epsilon) ||
x > (max(x1, x2) + epsilon) ||
x < (min(x3, x4) - epsilon) ||
x > (max(x3, x4) + epsilon))
        return false;
if (y < (min(y1, y2) - epsilon) ||
y > (max(y1, y2) + epsilon) ||
y < (min(y3, y4) - epsilon) ||
y > (max(y3, y4) + epsilon))
        return false;

A better test would be:
if (x (std::max(x1, x2) + epsilon) ||
x (std::max(x3, x4) + epsilon))
return false;
if (y (std::max(y1, y2) + epsilon) ||
y (std::max(y3, y4) + epsilon))
return false;

Where epsilon is say, 1e-5. This has the effect of testing against a line with a thickness of 2*epsilon accommodating any rounding errors.

// equations-to-code conversion

//float x1 = p1.x, x2 = p2.x, x3 = p3.x, x4 = p4.x;
//float y1 = p1.y, y2 = p2.y, y3 = p3.y, y4 = p4.y;

float d = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);
// If d is zero, there is no intersection

if (d == 0) return false;

// Get the x and y

float pre = (x1*y2 - y1*x2), post = (x3*y4 - y3*x4);

float x = ( pre * (x3 - x4) - (x1 - x2) * post ) / d;
float y = ( pre * (y3 - y4) - (y1 - y2) * post ) / d;

// Check if the x and y coordinates are within both lines

if ( x max(x1, x2) ||
x max(x3, x4) ) return false;
if ( y max(y1, y2) ||
y max(y3, y4) ) return false;

// Return the point of intersection
//But I don’t care about “where”, only “if”
//Point* ret = new Point();
//ret->x = x;
//ret->y = y;

return true;
}

void fixCollisions()
{
bigX=true; //Here’s the problem. Not with the hit detection math, but with the display
//of results
for (int i =0;i<wallUbound;i++)
{

if (intersection(FDX-cos(FDA),FDY-sin(FDA), //<--Right here
FDX+cos(FDA)+10,FDY+sin(FDA),
wallX[i]-cos(wallRot[i]),wallY[i]-sin(wallRot[i]),
wallX[i]+cos(wallRot[i]),wallY[i]+sin(wallRot[i])))
bigX=true;

}

}