ll1/cmd/ll1lex/flexer.go

package main

import "os"
import "io"
import "path/filepath"
import "fmt"
import "flag"
import "strings"
import "src.eruta.nl/beoran/ll1/flexer"

func help() {
	fmt.Printf("flexer usage: flexer [-o output.go] input.flex\n")
	fmt.Printf("\nGenerates a lexer in Go language.\n")
	os.Exit(1)
}

func showError(in string, err interface{}) {
	fmt.Fprintf(os.Stderr, "%s: error: %s\n", in, err)
}

func fatal(err error, code int) {
	fmt.Fprintf(os.Stderr, "flexer: error: %s\n", err)
	os.Exit(code)
}

func main() {
	outPtr := flag.String("o", "", "")
	flag.Parse()
	if flag.NArg() < 1 {
		help()
	}
	inName := flag.Arg(0)
	inFile, err := os.Open(inName)
	if err != nil {
		fatal(err, 1)
	}
	defer inFile.Close()
	buf, err := io.ReadAll(inFile)
	if err != nil {
		fatal(err, 2)
	}
	outName := inName + ".go"
	if outPtr != nil && *outPtr != "" {
		outName = *outPtr
	}
	abs, err := filepath.Abs(outName)
	if err != nil {
		fatal(err, 3)
	}
	parts := filepath.SplitList(abs)
	pkg := strings.TrimSuffix(filepath.Base(inName), filepath.Ext(inName))
	if len(parts) > 2 {
		pkg = parts[len(parts)-1]
	}
	tokens := flexer.LexFlexerInputString(inName, string(buf))
	fmt.Printf("package %s\n\n", pkg)
	for _, tok := range tokens {
		fmt.Printf("tok: %v\n", tok)
	}
}