Implement ImmArray.Find and ImmSet.TryGetValue.

Xledger.Collections.Test/TestImmArray.cs

@@ -146,6 +146,21 @@ public void TestCompareToRecord() {
         Assert.ThrowsAny<ArgumentException>(() => imm2 >= imm1);
     }
 
+    [Fact]
+    public void TestFind() {
+        var arr = Enumerable.Range(-1, 100).ToArray();
+        var imm = arr.ToImmArray();
+
+        Predicate<int> pred = i => i == -1;
+        Assert.Equal(Array.Find(arr, pred), imm.Find(pred));
+        pred = i => i == 12;
+        Assert.Equal(Array.Find(arr, pred), imm.Find(pred));
+        pred = i => i == 75;
+        Assert.Equal(Array.Find(arr, pred), imm.Find(pred));
+        pred = i => i == 1_000_000;
+        Assert.Equal(Array.Find(arr, pred), imm.Find(pred));
+    }
+
     public record Employee(int Id, string Name, decimal Salary);
 }
 

Xledger.Collections.Test/TestImmSet.cs

@@ -79,6 +79,25 @@ public void TestContains() {
         Assert.True(lst.Contains(3));
     }
 
+    [Fact]
+    public void TestTryGetValue() {
+        var imm = ImmSet.Of("foo", "bar", "baz");
+
+        var lookup = "food".Substring(0, 3);
+        var found = imm.TryGetValue(lookup, out var actual);
+        Assert.True(found);
+        Assert.NotSame(lookup, actual);
+        Assert.Equal(lookup, actual);
+
+        found = imm.TryGetValue("foo", out actual);
+        Assert.True(found);
+        Assert.Same("foo", actual);
+        Assert.Equal("foo", actual);
+
+        found = imm.TryGetValue("food", out actual);
+        Assert.False(found);
+    }
+
     [Fact]
     public void TestNoOps() {
         var imm = ImmSet.Of(7, 6, 5, 4);

Xledger.Collections/ImmArray.cs

@@ -121,6 +121,13 @@ public bool Contains(T item) {
         return this.data.Length > 0 && IndexOf(item) >= 0;
     }
 
+    /// <summary>
+    /// Returns the first matching element or default if none matches.
+    /// </summary>
+    public T Find(Predicate<T> pred) {
+        return Array.Find(this.data, pred);
+    }
+
     /// <inheritdoc />
     public int IndexOf(T item) {
         return Array.IndexOf<T>(this.data, item);

Xledger.Collections/ImmSet.cs

@@ -182,6 +182,13 @@ public bool SetEquals(IEnumerable<T> other) {
         }
     }
 
+    /// <summary>
+    /// Searches the set for a given value and returns the equal value it finds, if any.
+    /// </summary>
+    public bool TryGetValue(T equalValue, out T actualValue) {
+        return this.data.TryGetValue(equalValue, out actualValue);
+    }
+
     /// <inheritdoc />
     public override string ToString() {
         return $"[{string.Join(", ", this.data)}]";