;dist_atom a b
;
;
set a = $_
set sa = $struct<$a>
set b = $_
set sb = $struct<$b>

set x1 = (head($sa))	set sa = (tail($sa))
set y1 = (head($sa))	set sa = (tail($sa))		
set z1 = (head($sa))

set x2 = (head($sb))	set sb = (tail($sb))
set y2 = (head($sb))	set sb = (tail($sb))		
set z2 = (head($sb))

set x1 = ($x2-$x1)	set y1 = ($y2-$y1)	set z1 = ($z2-$z1)
set returned := (sqrt($x1^2 + $y1^2 + $z1^2))

