2.9: Implement Read-Parse-Print-Loop (RPPL)

ast/ast.go

@@ -66,6 +66,7 @@ func (ls *LetStatement) String() string {
 	out.WriteString(ls.TokenLiteral() + " ")
 	out.WriteString(ls.Name.String())
 	out.WriteString(" = ")
+	out.WriteString(ls.Value.String())
 
 	return out.String()
 }

repl/repl.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"io"
 	"monkey_interpreter/lexer"
-	"monkey_interpreter/token"
+	"monkey_interpreter/parser"
 )
 
 const PROMPT = ">> "
@@ -23,9 +23,20 @@ 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())
 		}
+
+		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")
 	}
 }