Using pattern matching to do pattern matching

matches.ktn

// Tests whether a string matches a file glob pattern, in
// which '*' matches any number of characters, '?' matches
// a single character, and anything else matches itself.
def matches:
  ->{ string pattern }
  if (string pattern {isEmpty} on &&): true
  else:
    false
    string peel ->{ ms ss }
    option ms: ->s
      pattern peel ->{ mp ps }
      option mp: ->p
        if (p '*' eqChar):
          drop
          (string ps matches)
          {ss pattern matches}
          |||
        else if ([s, '?'] p elemChar):
          drop
          ss ps matches

"foo.jpg" "f*.jp*g" matches sayBool  // true
"foo.jpg" "*.jp?"   matches sayBool  // true
"foo.jpg" "g*.jp?"  matches sayBool  // false

// Splits a vector safely into head and tail.
def peel:
  ->v
  if (v isEmpty):
    none []
  else:
    (v head) some
    (v tail)

// Lazy logical OR.
def |||:
  ->{ x f }
  if x: true else: f@