Add ToImmDict(Func<T, K> selectKey, Func<T, V> selectVal).

And `ToImmDict(Func<T, K> selectKey)` to simplify some conversion code instead of having to call `ToDictionary(selKey, selVal).ToImmDict()`. This avoids one dictionary copy as well.
xledger · Jan 31, 2025 · f2e0554 · f2e0554
1 parent 88fe70e
commit f2e0554
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diff --git a/Xledger.Collections.Test/TestImmDict.cs b/Xledger.Collections.Test/TestImmDict.cs
@@ -71,6 +71,34 @@ public void TestNoOps() {
         Assert.ThrowsAny<NotSupportedException>(() => idict.Remove(4));
         Assert.ThrowsAny<NotSupportedException>(() => ((System.Collections.ICollection)idict).CopyTo((Array)null, 0));
     }
+
+    [Fact]
+    public void TestSelectKey() {
+        var dct = Enumerable.Range(-100, 1_000).ToDictionary(i => i);
+        var imm = Enumerable.Range(-100, 1_000).ToImmDict(i => i);
+
+        for (int i = -1000; i < 2000; ++i) {
+            Assert.Equal(dct.ContainsKey(i), imm.ContainsKey(i));
+            if (dct.TryGetValue(i, out var dctValue)) {
+                imm.TryGetValue(i, out var immValue);
+                Assert.Equal(dctValue, immValue);
+            }
+        }
+    }
+
+    [Fact]
+    public void TestSelectKeySelectValue() {
+        var dct = Enumerable.Range(-100, 1_000).ToDictionary(i => i, i => (i * i).ToString());
+        var imm = Enumerable.Range(-100, 1_000).ToImmDict(i => i, i => (i * i).ToString());
+
+        for (int i = -1000; i < 2000; ++i) {
+            Assert.Equal(dct.ContainsKey(i), imm.ContainsKey(i));
+            if (dct.TryGetValue(i, out var dctValue)) {
+                imm.TryGetValue(i, out var immValue);
+                Assert.Equal(dctValue, immValue);
+            }
+        }
+    }
 }
 
 
diff --git a/Xledger.Collections/Extensions.cs b/Xledger.Collections/Extensions.cs
@@ -47,6 +47,23 @@ public static ImmDict<K, V> ToImmDict<K, V>(this IEnumerable<(K, V)> xs) {
         };
     }
 
+    public static ImmDict<K, T> ToImmDict<T, K>(this IEnumerable<T> xs, Func<T, K> selectKey) {
+        return xs switch {
+            null => ImmDict<K, T>.Empty,
+            _ => new ImmDict<K, T>(xs.ToDictionary(selectKey)),
+        };
+    }
+
+    public static ImmDict<K, V> ToImmDict<T, K, V>(
+        this IEnumerable<T> xs,
+        Func<T, K> selectKey,
+        Func<T, V> selectVal
+    ) {
+        return xs switch {
+            null => ImmDict<K, V>.Empty,
+            _ => new ImmDict<K, V>(xs.ToDictionary(selectKey, selectVal)),
+        };
+    }
     internal static T[] ArrayOf<T>(T[] arr) {
         return (T[])arr.Clone();
     }