(svn r4541) Add a type for slopes and replace many magic numbers by the appropriate enums

slope.h

@@ -0,0 +1,41 @@
+/* $Id$ */
+
+#ifndef SLOPE_H
+#define SLOPE_H
+
+typedef enum Slope {
+	SLOPE_FLAT  = 0x00,
+	SLOPE_W     = 0x01,
+	SLOPE_S     = 0x02,
+	SLOPE_E     = 0x04,
+	SLOPE_N     = 0x08,
+	SLOPE_STEEP = 0x10,
+	SLOPE_NW = SLOPE_N | SLOPE_W,
+	SLOPE_SW = SLOPE_S | SLOPE_W,
+	SLOPE_SE = SLOPE_S | SLOPE_E,
+	SLOPE_NE = SLOPE_N | SLOPE_E,
+	SLOPE_EW = SLOPE_E | SLOPE_W,
+	SLOPE_NS = SLOPE_N | SLOPE_S,
+	SLOPE_ELEVATED = SLOPE_N | SLOPE_E | SLOPE_S | SLOPE_W,
+	SLOPE_NWS = SLOPE_N | SLOPE_W | SLOPE_S,
+	SLOPE_WSE = SLOPE_W | SLOPE_S | SLOPE_E,
+	SLOPE_SEN = SLOPE_S | SLOPE_E | SLOPE_N,
+	SLOPE_ENW = SLOPE_E | SLOPE_N | SLOPE_W,
+	SLOPE_STEEP_W = SLOPE_STEEP | SLOPE_NWS,
+	SLOPE_STEEP_S = SLOPE_STEEP | SLOPE_WSE,
+	SLOPE_STEEP_E = SLOPE_STEEP | SLOPE_SEN,
+	SLOPE_STEEP_N = SLOPE_STEEP | SLOPE_ENW
+} Slope;
+
+static inline bool IsSteepSlope(Slope s)
+{
+	return (s & SLOPE_STEEP) != 0;
+}
+
+static inline Slope ComplementSlope(Slope s)
+{
+	assert(!IsSteepSlope(s));
+	return (Slope)(0xF ^ s);
+}
+
+#endif