edit:add-var ++~ {|n| + $n 1 }
edit:add-var --~ {|n| + $n 1 }

edit:add-var sign~ {|n|
  if (> $n 0) {
    put 1
  } elif (< $n 0) {
    put -1
  } else {
    put 0
  }
}
edit:add-var neg~ {|n| * $n -1 }
edit:add-var abs~ {|n|
  if (< $n 0) {
    neg $n
  } else {
    put $n
  }
}

edit:add-var sum~ {|@numbers|
  var s = 0
  each {|e| set s = (+ $s e) } (to-list $numbers)
}

fn -minmax {|t @numbers|
  var l = (to-list $@numbers)
  if (== (count $l) 0) {
    return
  }
  var m = $l[0]
  each {|n|
    if ($t $n $m) {
        set m = $n
    }
  } $l[1..]
  put $m
}

edit:add-var min~ {|@numbers| -minmax $'<~' $@numbers }
edit:add-var max~ {|@numbers| -minmax $'>~' $@numbers }