func format(args []string) {
flags := flag.NewFlagSet("", flag.ExitOnError)
write := flags.Bool("w", false, "write to file (instead of stdout)")
if len(args) == 0 {
log.SetPrefix("")
log.Fatal("Usage: pg fmt [flags] <file>\nFlags:\n\t-w write to file (instead of stdout)")
}
in := args[len(args)-1]
flags.Parse(args[:len(args)-1])
f, err := os.Open(in)
if err != nil {
log.Fatalf("cannot open file: %v", err)
}
defer f.Close()
src, err := ioutil.ReadAll(f)
if err != nil {
log.Fatalf("cannot read file: %v", err)
}
g, err := parser.Parse(src, in)
if err != nil {
log.Fatalf(err.Error())
}
if *write {
f.Close()
var buf bytes.Buffer
if err := printer.Fprint(&buf, g); err != nil {
log.Fatalf("cannot print grammar: %v", err)
}
if err = ioutil.WriteFile(in, buf.Bytes(), 0644); err != nil {
log.Fatalf("cannot write grammar: %v", err)
}
return
}
if err := printer.Fprint(os.Stdout, g); err != nil {
log.Fatalf("cannot print grammar: %v", err)
}
}
func TestFprint(t *testing.T) {
const expected = `Expr → Term "+" Expr | Term "-" Expr | Term | ε .
Term → Factor "*" Term | Factor "/" Term | Factor .
Factor → "(" Expr ")" | Number .
Number → Digit | Digit Number .
Digit → "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" .`
g := ast.Grammar([]*ast.Production{
{
Name: &ast.Name{Name: "Expr"},
Expr: ast.Alternative([]ast.Expression{
ast.Sequence([]ast.Expression{
&ast.Name{Name: "Term"},
&ast.Terminal{Terminal: "+"},
&ast.Name{Name: "Expr"},
}),
ast.Sequence([]ast.Expression{
&ast.Name{Name: "Term"},
&ast.Terminal{Terminal: "-"},
&ast.Name{Name: "Expr"},
}),
&ast.Name{Name: "Term"},
&ast.Epsilon{Epsilon: "e"},
}),
},
{
Name: &ast.Name{Name: "Term"},
Expr: ast.Alternative([]ast.Expression{
ast.Sequence([]ast.Expression{
&ast.Name{Name: "Factor"},
&ast.Terminal{Terminal: "*"},
&ast.Name{Name: "Term"},
}),
ast.Sequence([]ast.Expression{
&ast.Name{Name: "Factor"},
&ast.Terminal{Terminal: "/"},
&ast.Name{Name: "Term"},
}),
&ast.Name{Name: "Factor"},
}),
},
{
Name: &ast.Name{Name: "Factor"},
Expr: ast.Alternative([]ast.Expression{
ast.Sequence([]ast.Expression{
&ast.Terminal{Terminal: "("},
&ast.Name{Name: "Expr"},
&ast.Terminal{Terminal: ")"},
}),
&ast.Name{Name: "Number"},
}),
},
{
Name: &ast.Name{Name: "Number"},
Expr: ast.Alternative([]ast.Expression{
&ast.Name{Name: "Digit"},
ast.Sequence([]ast.Expression{
&ast.Name{Name: "Digit"},
&ast.Name{Name: "Number"},
}),
}),
},
{
Name: &ast.Name{Name: "Digit"},
Expr: ast.Alternative([]ast.Expression{
&ast.Terminal{Terminal: "0"}, &ast.Terminal{Terminal: "1"},
&ast.Terminal{Terminal: "2"}, &ast.Terminal{Terminal: "3"},
&ast.Terminal{Terminal: "4"}, &ast.Terminal{Terminal: "5"},
&ast.Terminal{Terminal: "6"}, &ast.Terminal{Terminal: "7"},
&ast.Terminal{Terminal: "8"}, &ast.Terminal{Terminal: "9"},
}),
},
})
var buf bytes.Buffer
if err := printer.Fprint(&buf, g); err != nil {
t.Errorf("error: %v", err)
}
if actual := buf.String(); actual != expected {
t.Errorf("got\n'%s'\nwant\n'%s'", actual, expected)
}
}