New interface and implementation to model function parameters

common-params.go

@@ -5,7 +5,26 @@
 package expr
 
 const (
+	paramCount     = "count"
+	paramItem      = "item"
 	paramParts     = "parts"
 	paramSeparator = "separator"
 	paramSource    = "source"
+	paramSuffix    = "suffix"
+	paramPrefix    = "prefix"
+	paramStart     = "start"
+	paramEnd       = "end"
+	paramValue     = "value"
+	paramEllipsis  = "..."
+	typeFilepath   = "filepath"
+	typeDirpath    = "dirpath"
 )
+
+// const (
+// 	typeInteger  = "int"
+// 	typeFloat    = "float"
+// 	typeString   = "string"
+// 	typeFraction = "fract"
+// 	typeList     = "list"
+// 	typeDict     = "dict"
+// )