From 86ef069848327f25c7118596e643ee55a3404577 Mon Sep 17 00:00:00 2001
From: Joseph Montanaro <jfmonty2@gmail.com>
Date: Thu, 18 Mar 2021 23:23:19 -0700
Subject: [PATCH] permutations iterator

---
 main.nim | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/main.nim b/main.nim
index 1bbc9ef..e2d2b78 100644
--- a/main.nim
+++ b/main.nim
@@ -1,4 +1,4 @@
-import options, sequtils, sugar
+import algorithm, options, sequtils, sugar
 
 
 type
@@ -18,6 +18,7 @@ type
   Board = object
     squares: array[1..16, Square]
     camels: array[Color, range[1..16]]
+    leader: Color
 
 
 proc `[]`(b: var Board, idx: range[1..16]): var Square =
@@ -58,18 +59,32 @@ proc advance(b: var Board, die: Die) =
   for i, c in b[startPos].camels:
     if c == color:
       let subStack = b[startPos].camels[i .. ^1]
-      b[endPos].camels.add(subStack)
       if prepend:
-        # figure out how to prepend a sequence to another sequence
+        b[endPos].camels.insert(subStack)
       else:
-        b[startPos].camels[i .. ^1] = @[]
+        b[endPos].camels.add(subStack)
+
+      b[startPos].camels[i .. ^1] = @[]
       for moved in subStack:
         b.camels[moved] = endPos
+      b.leader = b[b.camels.max][^1] # top camel in the last currently-occupied space
+
     break # breaking the outer loop here, not the inner
 
 
+iterator allPermutations[T](x: seq[T]): seq[T] =
+  # returns all permutations of a given array. Order is wonky but we don't care.
+  var workingCopy = x
+  yield workingCopy
+  while workingCopy.nextPermutation: # this mutates workingCopy
+    yield workingCopy
+  workingCopy = x
+  while workingCopy.prevPermutation:
+    yield workingCopy
+
+
 var b: Board
-# b.display(1, 5)
+b.display(1, 5)
 b.preRoll
 let c = b.dup(advance((cRed, range[1..3]3)))
 b.display(1, 5)