main.go

package main

import (
        "os"

        "github.com/alecthomas/participle"
        "github.com/alecthomas/participle/lexer"
        "github.com/alecthomas/repr"
)

var iniLexer = lexer.Must(lexer.Regexp(
        `(?m)` +
                `(\s+)` +
                `|(^[#;].*$)` +
                `|(?P<Unaryop>[!])` +
                `|(?P<Ident>[a-zA-Z][a-zA-Z_\d]*)` +
                `|(?P<String>"(?:\\.|[^"])*")` +
                `|(?P<Lparen>[\(])` +
                `|(?P<Rparen>[\)])` +
                `|(?P<Comma>[,])`,
))

type FullExpression struct {
        UnaryOp    *string       `{ @Unaryop }`
        Expression []*Expression `| @@`
}
type Expression struct {
        Function *string `@Ident`
        Lparen   *string `@Lparen`
        Arg      []*Arg  `{ @@ }`
        Rparen   *string `@Rparen`
}

type Arg struct {
        Arg   *string `@Ident | @String`
        Comma *string `| Comma`
}

func main() {
        parser, err := participle.Build(&FullExpression{}, participle.Lexer(iniLexer), participle.Unquote(iniLexer, "String"))
        if err != nil {
                panic(err)
        }
        myAST := &FullExpression{}
        err = parser.Parse(os.Stdin, myAST)
        if err != nil {
                panic(err)
        }
        repr.Println(myAST, repr.Indent("  "), repr.OmitEmpty(true))
}