improve error message in ReverseResolver and add cheat sheet

Author: memo33

README.md

@@ -133,6 +133,38 @@ You need to manually move the generated RUL2 files from the `target` directory
 to the correct locations in the `Controller` directory and then commit them into the git repository.
 For more information on Metarules, see https://github.com/memo33/metarules.
 
+#### Metarules Cheat Sheet
+
+Some functions for interacting with IDs and RUL2 code effectively are listed here.
+Type `sbt console` to enter the interactive REPL. Then:
+```scala
+resolve(Ard3~EW & Avenue~NS)                              // convert a metarule Tile to an ID
+// val result = IdTile(0x51021300,2,1)
+
+transduce(Ard3~EW | (Road ~> Ard3)~EW & Avenue~NS)        // convert a metarule to RUL2
+// 0x51020000,3,0,0x04008900,0,0=0x51020000,3,0,0x51021300,2,1
+// 0x51020000,1,0,0x04008900,0,0=0x51020000,1,0,0x51021300,0,0
+
+transduce(Sam2~(0,0,11,3) | Street~(11,2,2,0) | % | Sam2~(11,2,2,0))  // alternative syntax
+// 0x5E571200,3,0,0x5F500900,1,0=0x5E571200,3,0,0x5E576200,1,0
+
+preimage(0x57294745)                                      // convert an ID to a metarule Tile
+// val result = List(L2Rhw8c~(0,+2,0,-2) & Glr3~(3,0,0,1))
+
+preimage(IdTile(0x57294745,2,1))                          // convert an ID with rotation to a metarule Tile
+// val result = List(L2Rhw8c~(0,+2,0,-2) & Glr3~(1,3,0,0))
+
+preimage(resolve(Street~(2,2,2,2)))                       // result can be ambiguous if multiple definitions exist
+// val result = List(Street~(2,2,2,2), Street~(0,2,0,2) & Street~(2,0,2,0))
+
+(Road~(2,0,2,0)).symmetries                               // find the symmetries of a tile
+// val result = Dih2A((0,0), (2,0), (0,1), (2,1))
+(Ard3~ES & Ard3~NE).symmetries
+// val result = Cyc2D((0,0), (2,1))
+```
+
+See [metarules](https://github.com/memo33/metarules) for more details.
+
 ### Compiling Locale Files
 
 To convert all the translations contained in the directory [ltext/](ltext/)

src/main/scala/module/ReverseResolver.scala

@@ -13,9 +13,14 @@ class ReverseResolver private[module] (val reverseTileMap: collection.Map[Int, :
     case x: IdTile => x.id
     case id: Int => id
   }
+
   def isDefinedAt(idTile: IdTile | Int): Boolean = reverseTileMap.contains(toId(idTile))
+
   def apply(idTile: IdTile | Int): ::[Tile] = {
-    val fiber = reverseTileMap.apply(toId(idTile))
+    val id = toId(idTile)
+    val fiber =
+      try reverseTileMap.apply(id)
+      catch { case e: java.util.NoSuchElementException => throw new java.util.NoSuchElementException(f"0x$id%08X (ID not defined in any metarule ID resolver)") }
     idTile match {
       case x: IdTile => fiber.map(_ * x.rf).asInstanceOf[::[Tile]]
       case id: Int => fiber