add state-of-tic-tac-toe exercise

config.json

@@ -1614,6 +1614,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 3
+      },
+      {
+        "slug": "state-of-tic-tac-toe",
+        "name": "State of Tic-Tac-Toe",
+        "uuid": "8e616fd7-5368-4c18-bb94-b50e9bd1677b",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
       }
     ],
     "foregone": [

exercises/practice/state-of-tic-tac-toe/.docs/instructions.md

@@ -0,0 +1,101 @@
+# Instructions
+
+In this exercise, you're going to implement a program that determines the state of a [tic-tac-toe][] game.
+(_You may also know the game as "noughts and crosses" or "Xs and Os"._)
+
+The games is played on a 3×3 grid.
+Players take turns to place `X`s and `O`s on the grid.
+The game ends when one player has won by placing three of marks in a row, column, or along a diagonal of the grid, or when the entire grid is filled up.
+
+In this exercise, we will assume that `X` starts.
+
+It's your job to determine which state a given game is in.
+
+There are 3 potential game states:
+
+- The game is **ongoing**.
+- The game ended in a **draw**.
+- The game ended in a **win**.
+
+If the given board is invalid, throw an appropriate error.
+
+If a board meets the following conditions, it is invalid:
+
+- The given board cannot be reached when turns are taken in the correct order (remember that `X` starts).
+- The game was played after it already ended.
+
+## Examples
+
+### Ongoing game
+
+```text
+   |   |
+ X |   |
+___|___|___
+   |   |
+   | X | O
+___|___|___
+   |   |
+ O | X |
+   |   |
+```
+
+### Draw
+
+```text
+   |   |
+ X | O | X
+___|___|___
+   |   |
+ X | X | O
+___|___|___
+   |   |
+ O | X | O
+   |   |
+```
+
+### Win
+
+```text
+   |   |
+ X | X | X
+___|___|___
+   |   |
+   | O | O
+___|___|___
+   |   |
+   |   |
+   |   |
+```
+
+### Invalid
+
+#### Wrong turn order
+
+```text
+   |   |
+ O | O | X
+___|___|___
+   |   |
+   |   |
+___|___|___
+   |   |
+   |   |
+   |   |
+```
+
+#### Continued playing after win
+
+```text
+   |   |
+ X | X | X
+___|___|___
+   |   |
+ O | O | O
+___|___|___
+   |   |
+   |   |
+   |   |
+```
+
+[tic-tac-toe]: https://en.wikipedia.org/wiki/Tic-tac-toe

exercises/practice/state-of-tic-tac-toe/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "glennj"
+  ],
+  "files": {
+    "solution": [
+      "./state-of-tic-tac-toe.tcl"
+    ],
+    "test": [
+      "./state-of-tic-tac-toe.test"
+    ],
+    "example": [
+      ".meta/example.tcl"
+    ]
+  },
+  "blurb": "Determine the game state of a match of Tic-Tac-Toe.",
+  "source": "Created by Sascha Mann for the Julia track of the Exercism Research Experiment.",
+  "source_url": "https://github.com/exercism/research_experiment_1/tree/julia-dev/exercises/julia-1-a"
+}

exercises/practice/state-of-tic-tac-toe/.meta/example.tcl

@@ -0,0 +1,84 @@
+# This solution encodes the X and O positions into an integer.
+# The cells of the board are numbered like this:
+#   1 2 3
+#   4 5 6
+#   7 8 9
+#
+# Given a board like
+#   X X O
+#   O X .
+#   . X O
+# The value for X will have bits 1, 2, 5, 8 set == 010010011 == 147
+# The value for O will have bits 3, 4, 9    set == 100001100 == 268
+
+namespace eval StateOfTicTacToe {
+    namespace export gamestate
+
+    variable wins {
+        0b001001001
+        0b010010010
+        0b100100100
+        0b000000111
+        0b000111000
+        0b111000000
+        0b100010001
+        0b001010100
+    }
+
+    proc gamestate {board} {
+        lassign [parse $board] X O
+
+        switch [list [won $X] [won $O]] {
+            {true true} {error "Impossible board: game should have ended after the game was won"}
+
+            {true false} -
+            {false true} {return "win"}
+
+            default {
+                set xBits [bitCount $X]
+                set oBits [bitCount $O]
+                if {$xBits - $oBits > 1} then {error "Wrong turn order: X went twice"}
+                if {$xBits - $oBits < 0} then {error "Wrong turn order: O started"}
+                return [expr {$xBits + $oBits == 9 ? "draw" : "ongoing"}]
+            }
+        }
+    }
+
+    proc parse {board} {
+        set X 0
+        set O 0
+        set i 1
+
+        foreach cell [split [string cat {*}$board] ""] {
+            if {$cell in {X O}} then {setBit $cell $i}
+            incr i
+        }
+        return [list $X $O]
+    }
+
+    proc setBit {varname pos} {
+        upvar 1 $varname var
+        set var [expr {$var | (1 << ($pos - 1))}]
+    }
+
+    proc bitCount {n} {
+        set count 0
+        while {$n > 0} {
+            incr count [expr {$n & 1}]
+            set n [expr {$n >> 1}]
+        }
+        return $count
+    }
+
+    proc won {player} {
+        variable wins
+        foreach combo $wins {
+            if {($player & $combo) == $combo} {
+                return true
+            }
+        }
+        return false
+    }
+}
+
+namespace import StateOfTicTacToe::gamestate

exercises/practice/state-of-tic-tac-toe/.meta/tests.toml

@@ -0,0 +1,101 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[fe8e9fa9-37af-4d7e-aa24-2f4b8517161a]
+description = "Won games -> Finished game where X won via left column victory"
+
+[96c30df5-ae23-4cf6-bf09-5ef056dddea1]
+description = "Won games -> Finished game where X won via middle column victory"
+
+[0d7a4b0a-2afd-4a75-8389-5fb88ab05eda]
+description = "Won games -> Finished game where X won via right column victory"
+
+[bd1007c0-ec5d-4c60-bb9f-1a4f22177d51]
+description = "Won games -> Finished game where O won via left column victory"
+
+[c032f800-5735-4354-b1b9-46f14d4ee955]
+description = "Won games -> Finished game where O won via middle column victory"
+
+[662c8902-c94a-4c4c-9d9c-e8ca513db2b4]
+description = "Won games -> Finished game where O won via right column victory"
+
+[2d62121f-7e3a-44a0-9032-0d73e3494941]
+description = "Won games -> Finished game where X won via top row victory"
+
+[108a5e82-cc61-409f-aece-d7a18c1beceb]
+description = "Won games -> Finished game where X won via middle row victory"
+include = false
+
+[346527db-4db9-4a96-b262-d7023dc022b0]
+description = "Won games -> Finished game where X won via middle row victory"
+reimplements = "108a5e82-cc61-409f-aece-d7a18c1beceb"
+
+[a013c583-75f8-4ab2-8d68-57688ff04574]
+description = "Won games -> Finished game where X won via bottom row victory"
+
+[2c08e7d7-7d00-487f-9442-e7398c8f1727]
+description = "Won games -> Finished game where O won via top row victory"
+
+[bb1d6c62-3e3f-4d1a-9766-f8803c8ed70f]
+description = "Won games -> Finished game where O won via middle row victory"
+
+[6ef641e9-12ec-44f5-a21c-660ea93907af]
+description = "Won games -> Finished game where O won via bottom row victory"
+
+[ab145b7b-26a7-426c-ab71-bf418cd07f81]
+description = "Won games -> Finished game where X won via falling diagonal victory"
+
+[7450caab-08f5-4f03-a74b-99b98c4b7a4b]
+description = "Won games -> Finished game where X won via rising diagonal victory"
+
+[c2a652ee-2f93-48aa-a710-a70cd2edce61]
+description = "Won games -> Finished game where O won via falling diagonal victory"
+
+[5b20ceea-494d-4f0c-a986-b99efc163bcf]
+description = "Won games -> Finished game where O won via rising diagonal victory"
+
+[035a49b9-dc35-47d3-9d7c-de197161b9d4]
+description = "Won games -> Finished game where X won via a row and a column victory"
+
+[e5dfdeb0-d2bf-4b5a-b307-e673f69d4a53]
+description = "Won games -> Finished game where X won via two diagonal victories"
+
+[b42ed767-194c-4364-b36e-efbfb3de8788]
+description = "Drawn games -> Draw"
+
+[227a76b2-0fef-4e16-a4bd-8f9d7e4c3b13]
+description = "Drawn games -> Another draw"
+
+[4d93f15c-0c40-43d6-b966-418b040012a9]
+description = "Ongoing games -> Ongoing game: one move in"
+
+[c407ae32-4c44-4989-b124-2890cf531f19]
+description = "Ongoing games -> Ongoing game: two moves in"
+
+[199b7a8d-e2b6-4526-a85e-78b416e7a8a9]
+description = "Ongoing games -> Ongoing game: five moves in"
+
+[1670145b-1e3d-4269-a7eb-53cd327b302e]
+description = "Invalid boards -> Invalid board: X went twice"
+
+[47c048e8-b404-4bcf-9e51-8acbb3253f3b]
+description = "Invalid boards -> Invalid board: O started"
+
+[b1dc8b13-46c4-47db-a96d-aa90eedc4e8d]
+description = "Invalid boards -> Invalid board"
+include = false
+
+[6c1920f2-ab5c-4648-a0c9-997414dda5eb]
+description = "Invalid boards -> Invalid board: X won and O kept playing"
+reimplements = "b1dc8b13-46c4-47db-a96d-aa90eedc4e8d"
+
+[4801cda2-f5b7-4c36-8317-3cdd167ac22c]
+description = "Invalid boards -> Invalid board: players kept playing after a win"

exercises/practice/state-of-tic-tac-toe/state-of-tic-tac-toe.tcl

@@ -0,0 +1,3 @@
+proc gamestate {board} {
+    throw {NOT_IMPLEMENTED} "Implement this procedure."
+}