Debugging with an adverb

Often enough I need to debug my own code. The following adverb can be attached to any verb to trace its argument(s) and result:

t =: 1 : 0
	smoutput 'y:'
	smoutput y
	z =. u y
	smoutput 'result:'
	smoutput z
	z
:
	smoutput 'x:'
	smoutput x
	smoutput 'y:'
	smoutput y
	z =. x u y
	smoutput 'result:'
	smoutput z
	z
)

You can attach this t adverb to the right of any verb in your epression to have it traced:

   2 * 6 +t&*: 9
x:
36
y:
81
result:
117
234

A more compact form of the adverb is thinkable, too:

t2 =: 1 : 0
	smoutput y ; z=.   u y
	z
:
	smoutput x ; y ; z=. x u y
	z
)

   -t2/  1 2 3 4
+-+-+--+
|3|4|_1|
+-+-+--+
+-+--+-+
|2|_1|3|
+-+--+-+
+-+-+--+
|1|3|_2|
+-+-+--+
_2

While former "t" implementation may look more clumsely, it will still show you the arguments when the verb itself will fail -- often a helpful piece of information. The second one won't provide this.

(Up to and including J Rel. 4.x, the trace adverb can be affixed to not just conjunctions and adverbs, too. You will get the derived function's arguments and results traced. I.e., 6 +&t*: 9 works and show the 6 9 and 117. With later releases, this only holds for adverbs.)