basic lexing

cmd/repl/main.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"monkey/internal/lexer"
+	"monkey/internal/token"
+	"os"
+	"os/user"
+)
+
+const prompt = ">> "
+
+func main() {
+	user, err := user.Current()
+	if err != nil {
+		panic(err)
+	}
+	fmt.Printf("Hello %s! This is the Monkey programming language!\n",
+		user.Username)
+	fmt.Printf("Feel free to type in commands\n")
+	start(os.Stdin, os.Stdout)
+}
+
+func start(in io.Reader, out io.Writer) {
+	scanner := bufio.NewScanner(in)
+
+	for {
+		fmt.Fprintf(out, prompt)
+		scanned := scanner.Scan()
+		if !scanned {
+			return
+		}
+		line := scanner.Text()
+		l := lexer.New(line)
+		for tok := l.NextToken(); tok.Type != token.EOF; tok = l.NextToken() {
+			fmt.Fprintf(out, "%+v\n", tok)
+		}
+	}
+}