cats-parse graph query language experiment - hello world 4 / published by https://github.com/dacr/code-examples-manager #fc484393-ce97-44b6-bf6c-8f8addbf6a41/b01a03190dcf4ae4e4f6ee9f7fe8dc02489d6fc5

catsparse-hello-4.sc

// summary : cats-parse graph query language experiment - hello world 4
// keywords : scala, typelevel, cats-parse, hello-world, @testable
// publish : gist
// authors : David Crosson
// license : Apache License Version 2.0 (https://www.apache.org/licenses/LICENSE-2.0.txt)
// id : fc484393-ce97-44b6-bf6c-8f8addbf6a41
// created-on : 2025-03-13T14:22:01+01:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala "3.6.4"
//> using dep "org.typelevel::cats-parse:1.1.0"
//> using dep "com.lihaoyi::pprint:0.9.0"
// ---------------------

import cats.parse.{Parser0, Parser}
import cats.parse.Rfc5234.{lwsp, alpha}

case class Who(name: String)

val whitespaces = Parser.charIn(" \t\n\r").void.rep.void

extension [A](p: Parser[A]) {
  def token: Parser[A] = p <* (whitespaces|Parser.end)
}

val helloToken = Parser.ignoreCase("hello").token

val helloParser: Parser0[Option[Who]] = for {
  _    <- helloToken
  name <- alpha.rep.string.? <* whitespaces.?
} yield name.map(Who.apply)

val results = List(
  "hello david",
  "hello  joe  ",
  "hello"
).map(s => helloParser.parseAll(s))

pprint.pprintln(results)