added lua interpreter support for custom math functions

go/interpreter.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+
+	lua "github.com/yuin/gopher-lua"
+)
+
+// LUA interpreter, instanciated in main()
+var L *lua.LState
+
+var LuaFuncs map[string]int
+
+// called from lua to register a 1 arg math function
+func RegisterFuncOneArg(L *lua.LState) int {
+	function := L.ToString(1)
+	LuaFuncs[function] = 1
+	return 1
+}
+
+// called from lua to register a 1 arg math function
+func RegisterFuncTwoArg(L *lua.LState) int {
+	function := L.ToString(1)
+	LuaFuncs[function] = 2
+	return 1
+}
+
+func InitLua(L *lua.LState) {
+	LuaFuncs = map[string]int{}
+	L.SetGlobal("RegisterFuncOneArg", L.NewFunction(RegisterFuncOneArg))
+	L.SetGlobal("RegisterFuncTwoArg", L.NewFunction(RegisterFuncTwoArg))
+
+	if err := L.CallByParam(lua.P{
+		Fn:      L.GetGlobal("init"),
+		NRet:    0,
+		Protect: true,
+	}); err != nil {
+		panic(err)
+	}
+}
+
+func CallLuaFunc(L *lua.LState, funcname string, a float64, b float64) (float64, error) {
+	if LuaFuncs[funcname] == 1 {
+		// 1 arg variant
+		if err := L.CallByParam(lua.P{
+			Fn:      L.GetGlobal(funcname),
+			NRet:    1,
+			Protect: true,
+		}, lua.LNumber(a)); err != nil {
+			fmt.Println(err)
+			return 0, err
+		}
+	} else {
+		// 2 arg variant
+		if err := L.CallByParam(lua.P{
+			Fn:      L.GetGlobal(funcname),
+			NRet:    1,
+			Protect: true,
+		}, lua.LNumber(a), lua.LNumber(b)); err != nil {
+			return 0, err
+		}
+	}
+
+	// get result and cast to float64
+	if res, ok := L.Get(-1).(lua.LNumber); ok {
+		L.Pop(1)
+		return float64(res), nil
+	}
+
+	return 0, errors.New("function did not return a float64!")
+}