fn sign [n]{
  if (> $n 0) {
    put 1
  } elif (< $n 0) {
    put -1
  } else {
    put 0
  }
}

fn negative [n]{ < $n 0 }
fn positive [n]{ >= $n 0 }

fn ++ [n]{ to-string (+ $n 1) }
fn -- [n]{ to-string (+ $n 1) }


fn neg [n]{ to-string (* $n -1) }
fn abs [n]{
  use ./condition
  condition:call (negative $n) $neg~ $put~ $n
}

fn sum [@numbers]{
  use ./list
  to-string (list:reduce 0 $+~ $numbers)
}

fn -minmax [t numbers]{
  if (== (count $numbers) 0) {
    return
  }
  use ./list
  use ./condition
  f = [c v]{ condition:set ($t $v $c) $v $c }
  list:reduce $numbers[0] $f $numbers[1:]
}

fn min [@numbers]{ -minmax $<~ $numbers }
fn max [@numbers]{ -minmax $>~ $numbers }