Create a generic Apply function which applies any parameters and returns a function requring the discarded parameters.

Funcky.Test/FunctionalClass/ApplyTest.cs

@@ -0,0 +1,28 @@
+using static Funcky.Discard;
+
+namespace Funcky.Test.Extensions.FuncExtensions;
+
+public class ApplyTest
+{
+    [Fact]
+    public void CanApplyParametersInAnyOrder()
+    {
+        var func = Linear0;
+
+        var f1 = ((Func<int, int, int, int>)Linear0).Apply(__, __, 10);
+        var f2 = func.Apply(2, __, 7);
+        var f3 = Funcky.Extensions.FuncExtensions.Apply<int, int, int, int>(Linear0, __, __, 42);
+
+        Assert.Equal(30, f1(10, 2));
+        Assert.Equal(72, f2(10));
+        Assert.Equal(30, f3(10, 2));
+    }
+
+    [Fact]
+    public void Test2()
+    {
+    }
+
+    private static int Linear0(int a, int b, int c)
+        => a + (b * c);
+}

Funcky/Extensions/FuncExtensions/Apply.cs

@@ -0,0 +1,30 @@
+namespace Funcky.Extensions;
+
+public static partial class FuncExtensions
+{
+    // All overloads for Fuctions with 2 paramters.
+    public static Func<T1, TResult> Apply<T1, T2, TResult>(this Func<T1, T2, TResult> function, Unit arg1, T2 arg2)
+        => (a1) => function(a1, arg2);
+
+    public static Func<T2, TResult> Apply<T1, T2, TResult>(this Func<T1, T2, TResult> function, T1 arg1, Unit arg2)
+        => (a2) => function(arg1, a2);
+
+    // All overloads for Fuctions with 3 paramters.
+    public static Func<T2, T3, TResult> Apply<T1, T2, T3, TResult>(this Func<T1, T2, T3, TResult> function, T1 arg1, Unit arg2, Unit arg3)
+        => (a2, a3) => function(arg1, a2, a3);
+
+    public static Func<T1, T3, TResult> Apply<T1, T2, T3, TResult>(this Func<T1, T2, T3, TResult> function, Unit arg1, T2 arg2, Unit arg3)
+        => (a1, a3) => function(a1, arg2, a3);
+
+    public static Func<T1, T2, TResult> Apply<T1, T2, T3, TResult>(this Func<T1, T2, T3, TResult> function, Unit arg1, Unit arg2, T3 arg3)
+        => (a1, a2) => function(a1, a2, arg3);
+
+    public static Func<T3, TResult> Apply<T1, T2, T3, TResult>(this Func<T1, T2, T3, TResult> function, T1 arg1, T2 arg2, Unit arg3)
+        => a3 => function(arg1, arg2, a3);
+
+    public static Func<T2, TResult> Apply<T1, T2, T3, TResult>(this Func<T1, T2, T3, TResult> function, T1 arg1, Unit arg2, T3 arg3)
+        => a2 => function(arg1, a2, arg3);
+
+    public static Func<T1, TResult> Apply<T1, T2, T3, TResult>(this Func<T1, T2, T3, TResult> function, Unit arg1, T2 arg2, T3 arg3)
+        => a1 => function(a1, arg2, arg3);
+}

Funcky/PublicAPI.Unshipped.txt

@@ -1 +1,9 @@
 #nullable enable
+static Funcky.Extensions.FuncExtensions.Apply<T1, T2, T3, TResult>(this System.Func<T1, T2, T3, TResult>! function, Funcky.Unit arg1, Funcky.Unit arg2, T3 arg3) -> System.Func<T1, T2, TResult>!
+static Funcky.Extensions.FuncExtensions.Apply<T1, T2, T3, TResult>(this System.Func<T1, T2, T3, TResult>! function, Funcky.Unit arg1, T2 arg2, Funcky.Unit arg3) -> System.Func<T1, T3, TResult>!
+static Funcky.Extensions.FuncExtensions.Apply<T1, T2, T3, TResult>(this System.Func<T1, T2, T3, TResult>! function, Funcky.Unit arg1, T2 arg2, T3 arg3) -> System.Func<T1, TResult>!
+static Funcky.Extensions.FuncExtensions.Apply<T1, T2, T3, TResult>(this System.Func<T1, T2, T3, TResult>! function, T1 arg1, Funcky.Unit arg2, Funcky.Unit arg3) -> System.Func<T2, T3, TResult>!
+static Funcky.Extensions.FuncExtensions.Apply<T1, T2, T3, TResult>(this System.Func<T1, T2, T3, TResult>! function, T1 arg1, Funcky.Unit arg2, T3 arg3) -> System.Func<T2, TResult>!
+static Funcky.Extensions.FuncExtensions.Apply<T1, T2, T3, TResult>(this System.Func<T1, T2, T3, TResult>! function, T1 arg1, T2 arg2, Funcky.Unit arg3) -> System.Func<T3, TResult>!
+static Funcky.Extensions.FuncExtensions.Apply<T1, T2, TResult>(this System.Func<T1, T2, TResult>! function, Funcky.Unit arg1, T2 arg2) -> System.Func<T1, TResult>!
+static Funcky.Extensions.FuncExtensions.Apply<T1, T2, TResult>(this System.Func<T1, T2, TResult>! function, T1 arg1, Funcky.Unit arg2) -> System.Func<T2, TResult>!