September Morn Update

Task/Partial-function-application/Visual-Basic-.NET/partial-function-application-1.visual

@@ -0,0 +1,32 @@
+Module PartialApplication
+    Function fs(Of TSource, TResult)(f As Func(Of TSource, TResult), s As IEnumerable(Of TSource)) As IEnumerable(Of TResult)
+        ' This is exactly what Enumerable.Select does.
+        Return s.Select(f)
+    End Function
+
+    Function f1(x As Integer) As Integer
+        Return x * 2
+    End Function
+
+    Function f2(x As Integer) As Integer
+        Return x * x
+    End Function
+
+    ' The overload that takes a binary function and partially applies to its first parameter.
+    Function PartialApply(Of T1, T2, TResult)(f As Func(Of T1, T2, TResult), arg As T1) As Func(Of T2, TResult)
+        Return Function(arg2) f(arg, arg2)
+    End Function
+
+    Sub Main()
+        Dim args1 As Integer() = {0, 1, 2, 3}
+        Dim args2 As Integer() = {2, 4, 6, 8}
+
+        Dim fsf1 = PartialApply(Of Func(Of Integer, Integer), IEnumerable(Of Integer), IEnumerable(Of Integer))(AddressOf fs, AddressOf f1)
+        Dim fsf2 = PartialApply(Of Func(Of Integer, Integer), IEnumerable(Of Integer), IEnumerable(Of Integer))(AddressOf fs, AddressOf f2)
+
+        Console.WriteLine("fsf1, 0-3: " & String.Join(", ", fsf1(args1)))
+        Console.WriteLine("fsf1, evens: " & String.Join(", ", fsf1(args2)))
+        Console.WriteLine("fsf2, 0-3: " & String.Join(", ", fsf2(args1)))
+        Console.WriteLine("fsf2, evens: " & String.Join(", ", fsf2(args2)))
+    End Sub
+End Module