grammar_example.go

g := NewGrammar("Math", func(g GrammarInit) {
	Digit := Accept("0123456789")

	tNumber := NewLexItemType("Num")
	Number := OneOrMore(Digit).CaptureAsWithConversion(tNumber, func(str string) interface{} {
		val, _ := strconv.ParseInt(str, 10, 64)
		return val
	})

	tPlus := NewLexItemType("Plus")
	Plus := Accept("+").CaptureAs(tPlus)

	tEquality := NewLexItemType("Equal")
	Equality := Accept("=").CaptureAs(tEquality)

	g.Add(Number)
	g.Add(Plus)
	g.Add(Equality)
})

items := g.ParseString(`2 + 2 = 4`)
for _, item := range items {
	fmt.Printf("%-6s %-8T %#v\n", item.Type(), item.Value(), item.Value())
}

// Output:
// Num    int64    2
// Plus   string   "+"
// Num    int64    2
// Equal  string   "="
// Num    int64    4
//