charstream.js

function* CharStream(text) {
  const lines = text.split('\n')

  for (const row in lines) {
    const chars = lines[row].split('')
    
    for (const col in chars) {
       yield {token: chars[col], row, col}
    } 
  }
}

function CharStream(text) {
  const lines = text.split('\n')

  return lines.map((line, row) => {
    return line.split('').map((token, col) => ({token, row, col}))
  })
}

function InputStream(input) {
  let pos = 0
  let line = 1
  let col = 0

  return {
    next: () => {
      const ch = input.charAt(pos++)

      if (ch == "\n") {
        line++
        col = 0 
      } else {
        col++
      }

      return ch
    },
    peek: () => input.charAt(pos),
    eof: () => peek() == "",
    croak: () => {
      throw new Error(`${msg} (${line}:${col})`)
    }
  }
}