regexpeg

It is possible to express in PEG something like /\s(foo|bar|baz)\s.*/

A regular expression like /\s(foo|bar|baz)\s.*/ would match the following string:

football bartender bazooka baz to the end
                          ^^^^^^^^^^^^^^^

Is it possible to make a Parsing Expression Grammar rules that would parse the string in a similar fashion, splitting it into a Head and Tail?

Result <- Head Tail

football bartender bazooka baz to the end
         Head             |    Tail
Solution

  • Yes, it's achievable using PEG. Here's an example using pegjs:

    start = f:words space r:tail
{
   return [f, r];
}

tail = f:"baz" space r:words
{
   return r;
}

words = f:word r:(space word)*
{
   return [f].concat(r).flat().filter(n => n);
}

word = !tail w:$([A-Za-z]+)
{
   return w;
}

space = " "
{
   return;
}

    Output:

    [
   [
      "football",
      "bartender",
      "bazooka"
   ],
   [
      "to",
      "the",
      "end"
   ]
]