diff --git a/surface.cpp b/surface.cpp
index 3a119700..aa98e5f3 100644
--- a/surface.cpp
+++ b/surface.cpp
@@ -191,7 +191,7 @@ bool flag_clamp_max(ld& coord, ld maxv) {
   }
 
 bool flag_clamp(ld& coord, ld minv, ld maxv) {
-  return flag_clamp_min(coord, minv) & flag_clamp_max(coord, maxv);
+  return flag_clamp_min(coord, minv) && flag_clamp_max(coord, maxv);
   }
 
 bool flag_clamp_sym(ld& coord, ld v) {
@@ -209,13 +209,13 @@ bool inbound(ld& x, ld& y) {
       return flag_clamp(x, 90._deg, M_PI);
     
     case dsTractricoid:
-      return flag_clamp_min(x, 0) & flag_clamp_sym(y, M_PI);
+      return flag_clamp_min(x, 0) && flag_clamp_sym(y, M_PI);
     
     case dsKuen: 
-      return flag_clamp(x, 0, M_PI) & flag_clamp(y, 0, TAU);
+      return flag_clamp(x, 0, M_PI) && flag_clamp(y, 0, TAU);
     
     case dsHyperlike:
-      return flag_clamp_sym(x, M_PI) & flag_clamp_sym(y, hyperlike_bound());
+      return flag_clamp_sym(x, M_PI) && flag_clamp_sym(y, hyperlike_bound());
     
     default: 
       return true;