feat(gen): add symbol table

gen/symb.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"errors"
+	"strconv"
+	"strings"
+)
+
+type symbolType uintptr
+
+const (
+	// symbolTypeConst fields
+	//
+	//   0: const eval
+	symbolTypeConst symbolType = iota
+	// symbolTypeFunc fields
+	//
+	//   0: _para1_name, _para2_name, ...
+	//   1: replaceable eval
+	symbolTypeFunc
+)
+
+type symbol struct {
+	stype  symbolType
+	name   string
+	fields []string
+}
+
+func (s *symbol) replace(txt string, args ...string) (string, error) {
+	switch s.stype {
+	case symbolTypeConst:
+		return strings.ReplaceAll(txt, s.name, s.fields[0]), nil
+	case symbolTypeFunc:
+		//TODO: finish
+		return "", nil
+	}
+	return "", errors.New("unsupported symbol type " + strconv.Itoa(int(s.stype)))
+}