Default implementation of the inner radius in case LAPACK is not available....

Default implementation of the inner radius in case LAPACK is not available. Give the same value in case of a square 

Geo/MQuadrangle.cpp

@@ -294,6 +294,7 @@ double MQuadrangle::getOuterRadius()
 }
 double MQuadrangle::getInnerRadius()
 {
+#if defined(HAVE_LAPACK)
   // get the coordinates (x, y, z) of the 4 points defining the Quad
   double x[4] = {_v[0]->x(), _v[1]->x(), _v[2]->x(), _v[3]->x()};
   double y[4] = {_v[0]->y(), _v[1]->y(), _v[2]->y(), _v[3]->y()};
@@ -364,4 +365,30 @@ double MQuadrangle::getInnerRadius()
     }
   }
   return R;
+#else // HAVE_LAPACK
+  // Default implementation. Not sure that the following give exactly 
+  // the same value as the HAVE_LAPACK case !
+  // but same value for a square
+  
+  // Mid-point of each edge of the quadrangle
+  SPoint3 A(_v[0]->x()+_v[1]->x(),_v[0]->y()+_v[1]->y(),_v[0]->z()+_v[1]->z());
+  SPoint3 B(_v[1]->x()+_v[2]->x(),_v[1]->y()+_v[2]->y(),_v[1]->z()+_v[2]->z());
+  SPoint3 C(_v[2]->x()+_v[3]->x(),_v[2]->y()+_v[3]->y(),_v[2]->z()+_v[3]->z());
+  SPoint3 D(_v[3]->x()+_v[0]->x(),_v[3]->y()+_v[0]->y(),_v[3]->z()+_v[0]->z());
+  A*=0.5; B*=0.5; C*=0.5; D*=0.5;
+
+  // compute the length of the side
+  double a = A.distance(B);
+  double b = B.distance(C);
+  double c = C.distance(D);
+  double d = D.distance(A);
+
+  // perimeter
+  double s = a+b+c+d;
+  double halfs = 0.5*s;
+
+  return 0.25*sqrt( (a*c+b*d)*(a*d+b*c)*(a*b+c*d)/
+                   ((halfs-a)*(halfs-b)*(halfs-c)*(halfs-d))
+                  );
+#endif // HAVE_LAPACK
 }