Improve type system

core/values.go

@@ -0,0 +1,26 @@
+package elm
+
+import (
+	"golang.org/x/exp/constraints"
+)
+
+type INumber interface {
+    constraints.Float | constraints.Integer
+}
+
+type ElmValueType int32
+
+const (
+	NULLPTR ElmValueType = 0
+	NUMBER ElmValueType = 1
+)
+
+type ElmValue struct {
+	Type ElmValueType
+	Number int64
+	Null int64
+}
+
+func Number(val int64) ElmValue {
+	return ElmValue{Type: NUMBER, Number: val }
+}