WALTER syntax - combinators between expressions?

[DarkStar]

Would someone please explain these three WALTER statements?

set tcp_idx_margin	- / h 2 * scale 18

set tcp.trackidx  + + [0 0 this_tcp_indent] [folder_sec 0 0 0 0 0 0 1] * scale [0 0 18 100]

set tcp.trackidx 	?supercollapsed{0} + tcp.trackidx * scale [0 0 0 40]

It is the * between the expressions that is tripping me up; it does not look like Reverse Polish notation as I understand it. I could not find this syntax described in the docs.

Is the first line: tcp_idx_margin = ((h/2) * scale) - 18 ?
If so, should the RPN representation be - * / h 2 scale 18

And the third one:
if supercollapsed{0} == 1 then tcp.trackidx = (tcp.trackidx * scale) + [0 0 0 40]
ANd the RPN representation: + * tcp.trackidx scale [0 0 0 40]