diff -r 2c27f9be3fb9 -r f82a4facea8b src/slope.h
--- a/src/slope.h	Sat Oct 20 10:14:05 2007 +0000
+++ b/src/slope.h	Sat Oct 20 10:42:28 2007 +0000
@@ -48,9 +48,21 @@
 	CORNER_S = 1,
 	CORNER_E = 2,
 	CORNER_N = 3,
+	CORNER_END
 };
 
 /**
+ * Rangecheck for Corner enumeration.
+ *
+ * @param corner A #Corner.
+ * @return true iff corner is in a valid range.
+ */
+static inline bool IsValidCorner(Corner corner)
+{
+	return IS_INT_INSIDE(corner, 0, CORNER_END);
+}
+
+/**
  * Checks if a slope is steep.
  *
  * @param s The given #Slope.
@@ -79,6 +91,17 @@
 }
 
 /**
+ * Tests if a slope has a highest corner (i.e. one corner raised or a steep slope).
+ *
+ * @param s The #Slope.
+ * @return  true iff the slope has a highest corner.
+ */
+static inline bool HasSlopeHighestCorner(Slope s)
+{
+	return IsSteepSlope(s) || (s == SLOPE_W) || (s == SLOPE_S) || (s == SLOPE_E) || (s == SLOPE_N);
+}
+
+/**
  * Returns the highest corner of a slope (one corner raised or a steep slope).
  *
  * @pre      The slope must be a slope with one corner raised or a steep slope.
@@ -132,7 +155,7 @@
  */
 static inline Slope SlopeWithOneCornerRaised(Corner corner)
 {
-	assert(IS_INT_INSIDE(corner, 0, 4));
+	assert(IsValidCorner(corner));
 	return (Slope)(1 << corner);
 }
 
@@ -158,6 +181,8 @@
 	FOUNDATION_INCLINED_Y,       ///< The tile has an along Y-axis inclined foundation.
 	FOUNDATION_STEEP_LOWER,      ///< The tile has a steep slope. The lowerst corner is raised by a foundation to allow building railroad on the lower halftile.
 	FOUNDATION_STEEP_HIGHER,     ///< The tile has a steep slope. Three corners are raised by a foundation to allow building railroad on the higher halftile.
+
+	FOUNDATION_INVALID = 0xFF    ///< Used inside "rail_cmd.cpp" to indicate invalid slope/track combination.
 };
 
 /**