diff --git a/main.go b/main.go
index 72140f4a..36d41d99 100644
--- a/main.go
+++ b/main.go
@@ -1,7 +1,26 @@
 package main
 
 import "fmt"
-import "io/ioutil"
+import (
+	"io/ioutil"
+	"strings"
+	"regexp"
+	"strconv"
+)
+
+type Token struct {
+	typ  string
+	sval string
+}
+
+type Ast struct {
+	typ     string
+	ival    int
+	operand *Ast
+}
+
+var tokens []*Token
+var tokenIndex int
 
 func readFile(filename string) string {
 	bytes, err := ioutil.ReadFile(filename)
@@ -10,10 +29,91 @@ func readFile(filename string) string {
 	}
 	return string(bytes)
 }
-func main() {
-	s := readFile("/dev/stdin")
+
+func tokinize(s string) []*Token {
+	var r []*Token
+	trimed := strings.Trim(s, "\n")
+	chars := strings.Split(trimed, " ")
+	var regexNumber = regexp.MustCompile(`^[0-9]+$`)
+	for _, char := range chars {
+		debugPrint("char", char)
+		var tok *Token
+		if regexNumber.MatchString(char) {
+			tok = &Token{typ: "number", sval: strings.Trim(char, " \n")}
+		}
+
+		r = append(r, tok)
+	}
+
+	return r
+}
+
+func readToken() *Token {
+
+	if tokenIndex <= len(tokens)-1 {
+		r := tokens[tokenIndex]
+		tokenIndex++
+		return r
+	}
+	return nil
+}
+
+func parseUnaryExpr() *Ast {
+	tok := readToken()
+	ival, _ := strconv.Atoi(tok.sval)
+	return &Ast{
+		typ: "uop",
+		operand: &Ast{
+			typ:  "int",
+			ival: ival,
+		},
+	}
+}
+
+func parseExpr() *Ast {
+	ast := parseUnaryExpr()
+	return ast
+}
+
+func generate(ast *Ast) {
 	fmt.Println("\t.globl	main")
 	fmt.Println("main:")
-	fmt.Printf("\tmovl	$%s, %%eax\n", string(s))
+	emitAst(ast)
 	fmt.Println("\tret")
 }
+
+func emitAst(ast *Ast) {
+	if ast.typ == "uop" {
+		emitUop(ast)
+	}
+}
+
+func emitUop(ast *Ast) {
+	fmt.Printf("\tmovl	$%d, %%eax\n", ast.operand.ival)
+}
+
+func debugPrint(name string, v interface{}) {
+	fmt.Printf("# %s=%v\n", name, v)
+}
+
+func debugTokens(tokens []*Token) {
+	for _, tok := range tokens {
+		debugPrint("tok", tok)
+	}
+}
+
+func debugAst(ast *Ast) {
+	if ast.typ == "uop" {
+		debugPrint("ast.uop", ast.operand)
+	}
+}
+
+func main() {
+	s := readFile("/dev/stdin")
+	tokens = tokinize(s)
+	tokenIndex = 0
+	debugTokens(tokens)
+	ast := parseExpr()
+	debugAst(ast)
+	generate(ast)
+}