vic/fastparse_ext

---

vic/fastparse_ext.json

{
  "defaultBranch": "master",
  "description": "FastParse extensions",
  "fullName": "vic/fastparse_ext",
  "homepage": "http://www.lihaoyi.com/fastparse/",
  "language": "Scala",
  "name": "fastparse_ext",
  "pushedAt": "2025-07-15T04:40:24Z",
  "stargazersCount": 4,
  "updatedAt": "2025-07-15T04:40:27Z",
  "url": "https://github.com/vic/fastparse_ext"
}

FastParse extensions

Small utility extensions for fastparse.

Usage

import fastparse_ext._

Until

def Until(parser: => P[_]): P[Unit]

Moves the index just to just before parser succeeds.

Convenience for: (!parser ~ AnyChar).rep ~ &(parser)

UpTo

def UpTo[T]!(parser: => P[T]): P[T]

Ignores anything up to parser success.

Convenience for: (!parser ~ AnyChar).rep ~ parser

SetIndex

def SetIndex(index: Int)

Moves the parsing index to a certain position.

Warning: use with caution.

Within

def Within[I]!(outer: => P[_], inner: P[_] => P[I], endAtOuter: Boolean = false): P[I]
def Within2[O,I]!(outer: => P[O], inner: P[_] => P[I], endAtOuter: Boolean = false): P[_] => P[I]): P[(O, I)]
def NotWithin[O]!(outer: => P[O], inner: P[_] => P[I]): P[_] => P[_]): P[O]

Constrains an inner parser to run only inside an outer parser range.

IMPORTANT NOTE

Inner parser is always passed as partially applied function, because it will be run with a new index-delimited input.

Define your inner parser as a function def someInner[_: P] = ... and provide it partially applied: someInner(_)

If outer succeeds, the inner parser is run from outer’s start position, but it can never get past outer’s end position. By default, the end position is that of the inner parser, unless endAtOuter = true is explicitly given.

The result of Whithin2 is a tuple with the result of both parsers.

NotWithin succeeds only when inner fails inside of outer.

See [tests]!(fastparse_ext/test/src/fastparse_ext/FastparseExtTest.scala) for runnable examples.