Add enums section

content/enums.md

@@ -1,4 +1,57 @@
 ---
 title: Enums
 ---
-# Enums
+# Enums
+Enums in Nimrod are like enums in C, but are type-checked. There are no anonymous enums in Nimrod.
+
+``` nimrod
+type
+  # Note the Hungarian notation, used to avoid conflicts
+  CompassDirections = enum
+    cdNorth, cdEast, cdSouth, cdWest
+  # {.pure.} means it values must be prefixed with the enum's name
+  Colors {.pure.} = enum
+    Red = "FF0000", Green = (1, "00FF00"), Blue = "0000FF"
+  # Enums can have holes in them
+  # Not recommended, exists only for interoperability with C
+  Signals = enum
+    sigQuit = 3, sigAbort = 6, sigKill = 9
+
+# Iterates through the values
+for direction in cdNorth..cdWest:
+  # `ord()` returns the integer value of the enum
+  # `CompassDirections()` is the inverse of `ord()`
+  echo CompassDirections(ord(direction)), " ord: ", ord(direction)
+
+# `ord` gives the integer value, even if there are holes
+echo ord(sigQuit)
+
+# Enums are ordinal and have `inc` and `dec`
+var ordinal = low(int)
+inc ordinal
+dec ordinal
+echo high(char)
+
+when false:
+  var nonOrdinal = sigQuit
+  # `Signals` has holes and so isn't ordinal,
+  # so `inc` and `dec` don't work
+  inc nonOrdinal
+  dec nonOrdinal
+
+# The custom `$` makes it echo the hex value
+for color in Colors.Red..Colors.Blue:
+  echo color
+```
+
+```
+$ nimrod c -r enums.nim
+cdNorth ord: 0
+cdEast ord: 1
+cdSouth ord: 2
+cdWest ord: 3
+3
+FF0000
+00FF00
+0000FF
+```