Merge branch 'student' into solution

Author: Frederic Vogels

PiCross/DataStructures/Grid.cs

@@ -191,6 +191,13 @@ public static ISequence<T> Linearize<T>( this IGrid<T> grid )
 
     public static class Grid
     {
+        /// <summary>
+        /// Creates a new grid with the given size where each element is determined by <paramref name="initializer"/>.
+        /// </summary>
+        /// <typeparam name="T">Type of the elements of the grid.</typeparam>
+        /// <param name="size">Size of the grid.</param>
+        /// <param name="initializer">Function that determines what value the grid should take at each position.</param>
+        /// <returns>A new grid.</returns>
         public static IGrid<T> Create<T>( Size size, Func<Vector2D, T> initializer )
         {
             return new Grid<T>( size, initializer );

PiCross/DataStructures/Sequence.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using Cells;
@@ -11,7 +12,7 @@ namespace DataStructures
     /// populate the sequence with objects with <see cref="IVar"/>.
     /// </summary>
     /// <typeparam name="T">Element type.</typeparam>
-    public interface ISequence<out T>
+    public interface ISequence<out T> : IEnumerable<T>
     {
         /// <summary>
         /// Number of items in the sequence.
@@ -510,6 +511,16 @@ public IEnumerable<int> Indices
             }
         }
 
+        public IEnumerator<T> GetEnumerator()
+        {
+            return this.Items.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
         public IEnumerable<T> Items => Indices.Select( i => this[i] );
 
         public bool IsValidIndex( int index )

PiCross/Domain/PiCross/Puzzle.cs

@@ -7,10 +7,10 @@
 
 namespace PiCross
 {
-    public class AmbiguousConstraintsException : PiCrossException
+    public class InvalidConstraintsException : PiCrossException
     {
-        public AmbiguousConstraintsException()
-            : base( "Ambiguous constraints" )
+        public InvalidConstraintsException()
+            : base( "Invalid constraints" )
         {
             // NOP
         }
@@ -23,13 +23,15 @@ public AmbiguousConstraintsException()
     public sealed class Puzzle
     {
         /// <summary>
-        /// Creates a Puzzle from the constraints. Since a Puzzle
-        /// contains the solution, this method solves the given puzzle.
+        /// Creates a Puzzle from the constraints.
+        /// Internally, the puzzle is automatically solved.
+        /// If the constraints are ambiguous or contradictory,
+        /// an exception is thrown.
         /// </summary>
         /// <param name="columnConstraints">Column constraints.</param>
         /// <param name="rowConstraints">Row constraints.</param>
         /// <returns>A Puzzle with the given constraints.</returns>
-        /// <exception cref="AmbiguousConstraintsException">Thrown when the constraints
+        /// <exception cref="InvalidConstraintsException">Thrown when the constraints
         /// don't lead to a single solution.</exception>
         public static Puzzle FromConstraints( ISequence<Constraints> columnConstraints, ISequence<Constraints> rowConstraints )
         {
@@ -38,7 +40,7 @@ public static Puzzle FromConstraints( ISequence<Constraints> columnConstraints,
 
             if ( !solverGrid.IsSolved )
             {
-                throw new ArgumentException( "Ambiguous constraints" );
+                throw new InvalidConstraintsException();
             }
             else
             {
@@ -48,6 +50,25 @@ public static Puzzle FromConstraints( ISequence<Constraints> columnConstraints,
             }
         }
 
+        /// <summary>
+        /// Creates a Puzzle from the constraints.
+        /// Internally, the puzzle is automatically solved.
+        /// If the constraints are ambiguous or contradictory,
+        /// an exception is thrown.
+        /// </summary>
+        /// <param name="columnConstraints">Column constraints.</param>
+        /// <param name="rowConstraints">Row constraints.</param>
+        /// <returns>A Puzzle with the given constraints.</returns>
+        /// <exception cref="InvalidConstraintsException">Thrown when the constraints
+        /// don't lead to a single solution.</exception>
+        public static Puzzle FromConstraints( int[][] columnConstraints, int[][] rowConstraints )
+        {
+            var columnConstraintsAsSequence = Sequence.FromItems( columnConstraints.Select( Constraints.FromValues ).ToArray() );
+            var rowConstraintsAsSequence = Sequence.FromItems( rowConstraints.Select( Constraints.FromValues ).ToArray() );
+
+            return FromConstraints( columnConstraints: columnConstraintsAsSequence, rowConstraints: rowConstraintsAsSequence );
+        }
+
         /// <summary>
         /// Creates a Puzzle from a solution. The constraints
         /// will be inferred.

PiCross/Domain/PiCross/Square.cs

@@ -117,12 +117,15 @@ private Square()
 
         /// <summary>
         /// Symbol for this square.
+        /// Do NOT make use of this property to determine
+        /// what kind of Square it is. Instead, use equality, e.g.,
+        /// square == Square.UNKNOWN.
         /// </summary>
         public abstract char Symbol { get; }
 
         public override bool Equals( object obj )
         {
-            return this == obj;
+            return object.ReferenceEquals( this, obj );
         }
 
         public override int GetHashCode()