From bddc74eac884c3af50158bbf8d9017a2fdd0e82e Mon Sep 17 00:00:00 2001
From: Back Yu <yhfszb@gmail.com>
Date: Sat, 19 Jan 2019 12:12:09 +0800
Subject: [PATCH 1/3] Add support for method of map.

---
 runtime.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/runtime.go b/runtime.go
index d27d8bacf..a5e3b7320 100644
--- a/runtime.go
+++ b/runtime.go
@@ -96,6 +96,14 @@ func getFunc(val interface{}, i interface{}) (interface{}, bool) {
 		if value.IsValid() && value.CanInterface() {
 			return value.Interface(), true
 		}
+		// A map may have method too.
+		if v.NumMethod() > 0 {
+			name := reflect.ValueOf(i).String()
+			method := v.MethodByName(name)
+			if method.IsValid() && method.CanInterface() {
+				return method.Interface(), true
+			}
+		}
 	case reflect.Struct:
 		name := reflect.ValueOf(i).String()
 		method := v.MethodByName(name)

From 47bbccba33cd5fe056967222a4811d68e5a152c8 Mon Sep 17 00:00:00 2001
From: Back Yu <yhfszb@gmail.com>
Date: Sat, 19 Jan 2019 12:24:46 +0800
Subject: [PATCH 2/3] Improve the reflect of getFunc(...)

---
 runtime.go | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/runtime.go b/runtime.go
index a5e3b7320..51954d52d 100644
--- a/runtime.go
+++ b/runtime.go
@@ -83,7 +83,7 @@ func extract(val interface{}, i interface{}) (interface{}, bool) {
 	return nil, false
 }
 
-func getFunc(val interface{}, i interface{}) (interface{}, bool) {
+func getFunc(val interface{}, name string) (interface{}, bool) {
 	v := reflect.ValueOf(val)
 	d := v
 	if v.Kind() == reflect.Ptr {
@@ -92,20 +92,18 @@ func getFunc(val interface{}, i interface{}) (interface{}, bool) {
 
 	switch d.Kind() {
 	case reflect.Map:
-		value := d.MapIndex(reflect.ValueOf(i))
+		value := d.MapIndex(reflect.ValueOf(name))
 		if value.IsValid() && value.CanInterface() {
 			return value.Interface(), true
 		}
 		// A map may have method too.
 		if v.NumMethod() > 0 {
-			name := reflect.ValueOf(i).String()
 			method := v.MethodByName(name)
 			if method.IsValid() && method.CanInterface() {
 				return method.Interface(), true
 			}
 		}
 	case reflect.Struct:
-		name := reflect.ValueOf(i).String()
 		method := v.MethodByName(name)
 		if method.IsValid() && method.CanInterface() {
 			return method.Interface(), true

From 20aeaab3e07093d52d5d4a94cf6407f5409bdd77 Mon Sep 17 00:00:00 2001
From: Back Yu <yhfszb@gmail.com>
Date: Sat, 19 Jan 2019 16:13:20 +0800
Subject: [PATCH 3/3] Add tests for support method of map.

---
 eval_test.go | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/eval_test.go b/eval_test.go
index 308ddd4f4..2abd0fe36 100644
--- a/eval_test.go
+++ b/eval_test.go
@@ -21,6 +21,22 @@ type evalErrorTest struct {
 	err   string
 }
 
+type evalParams map[string]interface{}
+
+func (p evalParams) Max(a, b float64) float64 {
+	if a < b {
+		return b
+	}
+	return a
+}
+
+func (p evalParams) Min(a, b float64) float64 {
+	if a < b {
+		return a
+	}
+	return b
+}
+
 var evalTests = []evalTest{
 	{
 		"foo",
@@ -339,6 +355,16 @@ var evalTests = []evalTest{
 		map[string]interface{}{"foo": func(in string) string { return "hello " + in }},
 		"hello world",
 	},
+	{
+		"Max(a, b)",
+		evalParams{"a": 1.23, "b": 3.21},
+		3.21,
+	},
+	{
+		"Min(a, b)",
+		evalParams{"a": 1.23, "b": 3.21},
+		1.23,
+	},
 }
 
 var evalErrorTests = []evalErrorTest{