Improve Random interface

00_Common/dotnet/Games.Common/Randomness/IRandom.cs

@@ -6,47 +6,17 @@ namespace Games.Common.Randomness;
 public interface IRandom
 {
     /// <summary>
-    /// Gets a random <see cref="float" /> such that 0 <= n < 1.
+    /// Gets a random <see cref="float" /> such that 0 &lt;= n &lt; 1.
     /// </summary>
     /// <returns>The random number.</returns>
     float NextFloat();
 
     /// <summary>
-    /// Gets a random <see cref="float" /> such that 0 <= n < exclusiveMaximum.
+    /// Gets the <see cref="float" /> returned by the previous call to <see cref="NextFloat" />.
-    /// </summary>
-    /// <returns>The random number.</returns>
-    float NextFloat(float exclusiveMaximum);
-
-    /// <summary>
-    /// Gets a random <see cref="float" /> such that inclusiveMinimum <= n < exclusiveMaximum.
-    /// </summary>
-    /// <returns>The random number.</returns>
-    float NextFloat(float inclusiveMinimum, float exclusiveMaximum);
-
-    /// <summary>
-    /// Gets a random <see cref="int" /> such that 0 <= n < exclusiveMaximum.
-    /// </summary>
-    /// <returns>The random number.</returns>
-    int Next(int exclusiveMaximum);
-
-    /// <summary>
-    /// Gets a random <see cref="int" /> such that inclusiveMinimum <= n < exclusiveMaximum.
-    /// </summary>
-    /// <returns>The random number.</returns>
-    int Next(int inclusiveMinimum, int exclusiveMaximum);
-
-    /// <summary>
-    /// Gets the previous random number as a <see cref="float" />.
     /// </summary>
     /// <returns>The previous random number.</returns>
     float PreviousFloat();
 
-    /// <summary>
-    /// Gets the previous random number as an <see cref="int" />.
-    /// </summary>
-    /// <returns>The previous random number.</returns>
-    int Previous();
-
     /// <summary>
     /// Reseeds the random number generator.
     /// </summary>

00_Common/dotnet/Games.Common/Randomness/IRandomExtensions.cs

@@ -0,0 +1,91 @@
+using System;
+
+namespace Games.Common.Randomness;
+
+/// <summary>
+/// Provides extension methods to <see cref="IRandom" /> providing random numbers in a given range.
+/// </summary>
+/// <value></value>
+public static class IRandomExtensions
+{
+    /// <summary>
+    /// Gets a random <see cref="float" /> such that 0 &lt;= n &lt; exclusiveMaximum.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    public static float NextFloat(this IRandom random, float exclusiveMaximum) =>
+        Scale(random.NextFloat(), exclusiveMaximum);
+
+    /// <summary>
+    /// Gets a random <see cref="float" /> such that inclusiveMinimum &lt;= n &lt; exclusiveMaximum.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    public static float NextFloat(this IRandom random, float inclusiveMinimum, float exclusiveMaximum) =>
+        Scale(random.NextFloat(), inclusiveMinimum, exclusiveMaximum);
+
+    /// <summary>
+    /// Gets a random <see cref="int" /> such that 0 &lt;= n &lt; exclusiveMaximum.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    public static int Next(this IRandom random, int exclusiveMaximum) => ToInt(random.NextFloat(exclusiveMaximum));
+
+    /// <summary>
+    /// Gets a random <see cref="int" /> such that inclusiveMinimum &lt;= n &lt; exclusiveMaximum.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    public static int Next(this IRandom random, int inclusiveMinimum, int exclusiveMaximum) =>
+        ToInt(random.NextFloat(inclusiveMinimum, exclusiveMaximum));
+
+    /// <summary>
+    /// Gets the previous unscaled <see cref="float" /> (between 0 and 1) scaled to a new range:
+    /// 0 &lt;= x &lt; <paramref name="exclusiveMaximum" />.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    public static float PreviousFloat(this IRandom random, float exclusiveMaximum) =>
+        Scale(random.PreviousFloat(), exclusiveMaximum);
+
+    /// <summary>
+    /// Gets the previous unscaled <see cref="float" /> (between 0 and 1) scaled to a new range:
+    /// <paramref name="inclusiveMinimum" /> &lt;= n &lt; <paramref name="exclusiveMaximum" />.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    public static float PreviousFloat(this IRandom random, float inclusiveMinimum, float exclusiveMaximum) =>
+        Scale(random.PreviousFloat(), inclusiveMinimum, exclusiveMaximum);
+
+    /// <summary>
+    /// Gets the previous unscaled <see cref="float" /> (between 0 and 1) scaled to an <see cref="int" /> in a new
+    /// range: 0 &lt;= n &lt; <paramref name="exclusiveMaximum" />.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    public static int Previous(this IRandom random, int exclusiveMaximum) =>
+        ToInt(random.PreviousFloat(exclusiveMaximum));
+
+    /// <summary>
+    /// Gets the previous unscaled <see cref="float" /> (between 0 and 1) scaled to an <see cref="int" /> in a new
+    /// range: <paramref name="inclusiveMinimum" /> &lt;= n &lt; <paramref name="exclusiveMaximum" />.
+    /// <returns>The random number.</returns>
+    public static int Previous(this IRandom random, int inclusiveMinimum, int exclusiveMaximum) =>
+        ToInt(random.PreviousFloat(inclusiveMinimum, exclusiveMaximum));
+
+    private static float Scale(float zeroToOne, float exclusiveMaximum)
+    {
+        if (exclusiveMaximum <= 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(exclusiveMaximum), "Must be greater than 0.");
+        }
+
+        return Scale(zeroToOne, 0, exclusiveMaximum);
+    }
+
+    private static float Scale(float zeroToOne, float inclusiveMinimum, float exclusiveMaximum)
+    {
+        if (exclusiveMaximum <= inclusiveMinimum)
+        {
+            throw new ArgumentOutOfRangeException(nameof(exclusiveMaximum), "Must be greater than inclusiveMinimum.");
+        }
+
+        var range = exclusiveMaximum - inclusiveMinimum;
+        return zeroToOne * range + inclusiveMinimum;
+    }
+
+    private static int ToInt(float value) => (int)Math.Floor(value);
+}

00_Common/dotnet/Games.Common/Randomness/RandomNumberGenerator.cs

@@ -2,6 +2,7 @@ using System;
 
 namespace Games.Common.Randomness;
 
+/// <inheritdoc />
 public class RandomNumberGenerator : IRandom
 {
     private Random _random;
@@ -13,38 +14,9 @@ public class RandomNumberGenerator : IRandom
         _random = new Random((int)(DateTime.UtcNow.Ticks / TimeSpan.TicksPerSecond));
     }
 
-    public float NextFloat() => NextFloat(1);
+    public float NextFloat() => _previous = (float)_random.NextDouble();
-
-    public float NextFloat(float exclusiveMaximum)
-    {
-        if (exclusiveMaximum <= 0)
-        {
-            throw new ArgumentOutOfRangeException(nameof(exclusiveMaximum), "Must be greater than 0.");
-        }
-
-        return NextFloat(0, exclusiveMaximum);
-    }
-
-    public float NextFloat(float inclusiveMinimum, float exclusiveMaximum)
-    {
-        if (exclusiveMaximum <= inclusiveMinimum)
-        {
-            throw new ArgumentOutOfRangeException(nameof(exclusiveMaximum), "Must be greater than inclusiveMinimum.");
-        }
-
-        var range = exclusiveMaximum - inclusiveMinimum;
-        return _previous = ((float)_random.NextDouble()) * range + inclusiveMinimum;
-    }
-
-    public int Next(int exclusiveMaximum) => ToInt(NextFloat(exclusiveMaximum));
-
-    public int Next(int inclusiveMinimum, int exclusiveMaximum) => ToInt(NextFloat(inclusiveMinimum, exclusiveMaximum));
 
     public float PreviousFloat() => _previous;
 
-    public int Previous() => ToInt(_previous);
-
-    private static int ToInt(float value) => (int)Math.Floor(value);
-
     public void Reseed(int seed) => _random = new Random(seed);
 }