[Unicon-group] {/x:=y; x} equivalent with only one x

[Majorinc, Kazimir]

I'm sure Steve will not like macro, but without it, it is pretty "iconish," 
and it seems to work to some extent. There is one related question at the 
end of this post.

#============================================================
$define initialized_empty :=:tempty):=((/tempty&[])|tempty)
$define let (
procedure main()

  # full expression examples

 writes("expression is >",(x:=:s):=((/s&"first goes,")|s),"< ")
 write("and x is >",x,"<")
 writes("expression is >",(x:=:s):=((/s&"second doesn't")|s),"< ")
 write("and x is >",x,"<")
  # macro examples

 x:=&null
 writes("before first execution x=",image(x))
 writes(", expression is ",image(let x initialized_empty) )
 write(", after execution x is ",image(x),".")
 x:=[1]
 writes("before second execution x=",image(x))
 writes(", expression is ",image(let x initialized_empty) )
 write(", after execution x is ",image(x),".")
 end
#=================================================
Output with wiconix
=====================================================
expression is >first goes,< and x is >first goes,<
expression is >first goes,< and x is >first goes,<
before first execution x=&null, expression is list_1(0), after execution x 
is list_1(0).
before second execution x=list_3(1), expression is list_3(1), after 
execution x is list_3(1).
#=================================================

Output with nticonix is almost the same, but in last line, it is list_2 
instead of list_3. Even if I catch window output with my Scite editor, it 
is list_2. Same wicont and nticont. Where that list gone if window is opened?

----
Kazimir Majorinc, Zagreb, Croatia