print parsing result in repl

ast/ast.go

@@ -58,3 +58,20 @@ func (cc *ConsCell) String() string {
 type Program struct {
 	SExpressions []Cell
 }
+
+func (p *Program) TokenLiteral() string {
+	if len(p.SExpressions) > 0 {
+		return p.SExpressions[0].TokenLiteral()
+	}
+	return ""
+}
+
+func (p *Program) String() string {
+	var out bytes.Buffer
+
+	for _, s := range p.SExpressions {
+		out.WriteString(s.String())
+	}
+
+	return out.String()
+}

repl/repl.go

@@ -6,7 +6,7 @@ import (
 	"io"
 
 	"github.com/JunNishimura/go-lisp/lexer"
-	"github.com/JunNishimura/go-lisp/token"
+	"github.com/JunNishimura/go-lisp/parser"
 )
 
 const PROMPT = ">> "
@@ -23,9 +23,21 @@ func Start(in io.Reader, out io.Writer) {
 
 		line := scanner.Text()
 		l := lexer.New(line)
+		p := parser.New(l)
 
-		for tok := l.NextToken(); tok.Type != token.EOF; tok = l.NextToken() {
-			fmt.Printf("%+v\n", tok)
+		program := p.ParseProgram()
+		if len(p.Errors()) != 0 {
+			printParserErrors(out, p.Errors())
+			continue
 		}
+
+		io.WriteString(out, program.String())
+		io.WriteString(out, "\n")
+	}
+}
+
+func printParserErrors(out io.Writer, errors []string) {
+	for _, msg := range errors {
+		io.WriteString(out, "\t"+msg+"\n")
 	}
 }