ccorcos

const between = (l, p, r) => sequence([l, p, r]).map(v => v[1])

ccorcos

const not = parser =>
  new Parser(stream =>
    parser.run(stream)
    .fold(
      (value, s) => new Failure('not failed', stream),
      (value, s) =>
        stream.length > 0
          ? new Success(stream.head(), stream.move(1))
          : new Failure('unexpected end', stream)))

ccorcos

const string = str => sequence(str.split('').map(char))

ccorcos

const zeroOrMore = parser =>
  new Parser(stream =>
    parser.run(stream)
    .fold(
      (value, s) => zeroOrMore(parser).map(rest => [value].concat(rest)).run(s),
      (value, s) => new Success([], stream)))

ccorcos

const lookahead = parser =>
  new Parser(stream =>
    parser.run(stream)
    .fold(
      (v) => new Success(v, stream),
      (v) => new Failure(v, stream)))

ccorcos

const maybe = parser =>
  new Parser(stream =>
    parser.run(stream)
    .fold(
      (v, s) => new Success(v, s),
      (v, s) => new Success(null, stream)))

ccorcos

const always = value => 
  new Parser(stream => new Success(value, stream))

const never = value => 
  new Parser(stream => new Failure(value, stream))

const append = (p1, p2) => 
  p1.chain(vs => p2.map(v => vs.concat([v])))

const concat = (p1, p2) =>

ccorcos

const either = list =>
  new Parser(stream => {
    for (let i = 0; i < list.length; i++) {
      const parser = list[i]
      const result = parser.run(stream)
      if (result instanceof Success) {
        return result
      }
    }
    return new Failure('either failed', stream)

ccorcos

char('a')
.chain(v1 => 
  char('b')
  .chain(v2 =>
    char('c')
    .map(v3 => [v1, v2, v3])
  )
)
.run('abc')
.fold(

ccorcos

char('a')
.chain(v => char('b'))
.chain(v => char('c'))
.run('abc')
.fold(
  v => console.log('success', v)
  e => console.log('error', e)
)
// => success c