m||n -- joins nets or strings by concatenating them vertically. The baseline of the result is the baseline of the first one.
In this example, we build a large net with arrows to indicate the location of the baseline.
i1 : x = "x" | "3"^1
3
o1 = x
|
i2 : "<--- " | ( x || "" || x ) | " --->"
3
o2 = <--- x --->
3
x
|