init + lexer

main.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"os"
+)
+
+var (
+	file string
+)
+
+func main() {
+	flag.Parse()
+	args := flag.Args()
+
+	if len(args) > 1 {
+		fmt.Printf("Usage: %s [script]", args[0])
+		os.Exit(64)
+	} else if len(args) == 1 {
+		runFile(args[0])
+	} else {
+		repl()
+	}
+}
+
+func runFile(filename string) {
+	bs, err := os.ReadFile(filename)
+	if err != nil {
+		fmt.Printf("unable to read file '%s':\n\t%s", filename, err.Error())
+		os.Exit(1)
+	}
+
+	if run(string(bs)) {
+		os.Exit(65)
+	}
+}
+
+func repl() {
+	s := bufio.NewScanner(os.Stdin)
+	for {
+		fmt.Printf("repl> ")
+		s.Scan()
+		text := s.Text()
+
+		if text == ":q" {
+			return
+		}
+
+		run(text)
+		if err := s.Err(); err != nil {
+			panic(err)
+		}
+	}
+}
+
+func run(source string) bool {
+	s := newScanner(source)
+	tokens, ok := s.ScanTokens()
+	if !ok {
+		return true
+	}
+
+	for _, token := range tokens {
+		fmt.Println(token)
+	}
+
+	return false
+}
+
+func reportErr(line int, message string) {
+	report(line, "", message)
+}
+
+func report(line int, where, message string) {
+	fmt.Printf("[line %d] Error%s: %s\n", line, where, message)
+}