Monadic absolute vаlue

Rеturns the absolute vаlue of a numeral or temporal, rеturns null for null.

Syntax: abs <x>; abs[<x>]

o)abs 1.0 -10.5 0
1 10.5 0
o)abs -11:08
11:08

abs is fully atomic:

o)abs (1;-2 3;-4 5 6.0)
1
2 3
4 5 6f