history: update

Author: changkun

history/contracts-interface-compare.go.txt renamed to history/202003.go2.txt

@@ -0,0 +1,41 @@
+// Copyright 2020 Changkun Ou. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package history
+
+// type parameters
+
+type Ordered interface {
+	type int, int8, int16, int32, int64,
+		uint, uint8, uint16, uint32, uint64, uintptr,
+		float32, float64,
+		string
+}
+
+// Max returns the maximum among all parameters
+func Max[type T Ordered](v0 T, vn ...T) T {
+	switch l := len(vn); {
+	case l == 0:
+		return v0
+	case l == 1:
+		if v0 > vn[0] { return v0 }
+		return vn[0]
+	default:
+		vv := Max(vn[0], vn[1:]...)
+		if v0 > vv { return v0 }
+		return vv
+	}
+}
+
+// a more complex example:
+
+type I1 [type P1] interface {
+    m1(x P1)
+}
+type I2 [type P1, P2] interface {
+    m2(x P1) P2
+    type int, float64
+}
+
+func F[type P1 I1[P1], P2 I2[P1, P2]] (x P1, y P2) {}