cats-parse graph query language experiment - hello world 3 / published by https://github.com/dacr/code-examples-manager #92da5000-0627-4ec2-b6e9-77bbbd9d0f26/9b08b55ce9d5e5ea734b34e50455104bbfeb8321

catsparse-hello-3.sc

// summary : cats-parse graph query language experiment - hello world 3
// 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 : 92da5000-0627-4ec2-b6e9-77bbbd9d0f26
// 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 helloToken = Parser.ignoreCase("hello").surroundedBy(lwsp)

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


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

pprint.pprintln(results)