[Jprogramming] Difficulties understanding a sentence with the compose-conjunction

[Thomas Bulka]

Hello everyone,

I stumbled across another understanding problem during my efforts to 
learn J. I do currently struggle with a sentence defined in the essay "A 
Composition on Composition":

https://code.jsoftware.com/wiki/Fifty_Shades_of_J/Chapter_2

In this essay the sentence "to" is defined like this:

to =: -.&i.~,]

It works as expected and generates a list of integers from x to y 
(dyadic use). I do unterstand (I think) the use of the &-conjunction in 
this sentence, but what I don't get is the i.~,]-part. My (obviously 
wrong) interpretation goes like this - (s[n] denotes my assumption on 
the different steps of evaluation when called with, say, 12 as the 
y-parameter):

s1 =: i.~,]
s2 =: i.~,12      NB. ] denotes the y-parameter
s3 =: i.~12       NB. Now y is raveled
s4 =: 12 i. 12   NB. By using ~ 12 is the x- and y-parameter of i

The result of the final step would be zero (according to my 
understanding), but explicitly calling "s1 12" gives the result 0 12. 
Neither do I understand that result, nor do I understand, how this 
contributes to the to-sentence defined above. As you can see, I'm 
totally lost here and would very much appreciate any explanation on how 
to interpret that sentence correctly.

Please excuse the lengthy description of my misunderstanding, but I 
tried to describe my train of thought to make as clear as possible, 
where my difficulties in understanding are.

Thank you very much in advance!

Kind regards,

Thomas