[Jprogramming] Self-reference in an explicit definition

[Ian Clark]

Let's define a verb: max which can be used either dyadically:

   5 max 7
7

or monadically:

   max 5 7
7

Can somebody explain to me please
(for the purpose of completing
http://www.jsoftware.com/jwiki/Vocabulary/dollarco )
why this works:

max=: $:/ : >.

but this doesn't:

max=: 3 : 0
$:/y
:
x>.y
)

The explicit version (which to me looks equivalent to the tacit one)
does not work with a noun longer than 1 atom:

   max 7
7
   max 5 7
|stack error: max
|       $:/y