diff --git a/tools/lgf-gen.cc b/tools/lgf-gen.cc
--- a/tools/lgf-gen.cc
+++ b/tools/lgf-gen.cc
@@ -65,7 +65,7 @@
 double totalLen(){
   double tlen=0;
   for(EdgeIt e(g);e!=INVALID;++e)
-    tlen+=sqrt((coords[g.v(e)]-coords[g.u(e)]).normSquare());
+    tlen+=std::sqrt((coords[g.v(e)]-coords[g.u(e)]).normSquare());
   return tlen;
 }
 
@@ -188,7 +188,7 @@
       (q.x * q.x + q.y * q.y) * (r.x * p.y - p.x * r.y) +
       (r.x * r.x + r.y * r.y) * (p.x * q.y - q.x * p.y);
 
-    return d / (2 * a) + sqrt((d * d + e * e) / (4 * a * a) + f / a);
+    return d / (2 * a) + std::sqrt((d * d + e * e) / (4 * a * a) + f / a);
   }
 
   inline bool circle_form(const Point& p, const Point& q, const Point& r) {
@@ -206,7 +206,7 @@
     double a = q.x - p.x;
     double b = (q.x - sx) * p.y - (p.x - sx) * q.y;
     double d = (q.x - sx) * (p.x - sx) * (p - q).normSquare();
-    return (b - sqrt(d)) / a;
+    return (b - std::sqrt(d)) / a;
   }
 
   struct YLess {
@@ -813,7 +813,7 @@
   std::cout << "Number of arcs    : " << countEdges(g) << std::endl;
   double tlen=0;
   for(EdgeIt e(g);e!=INVALID;++e)
-    tlen+=sqrt((coords[g.v(e)]-coords[g.u(e)]).normSquare());
+    tlen+=std::sqrt((coords[g.v(e)]-coords[g.u(e)]).normSquare());
   std::cout << "Total arc length  : " << tlen << std::endl;
 
   if(ap["eps"])