[clean-list] Help with list comprehension

[Frantisek Fuka]

I'm working my way through the Clean Book and I'm stumped by exercise 5 
in Chapter 3.10:

"Write a list comprehension for generating all permutations of some 
input list."

The list of length "len" has "len!" permutations so it seems to me that 
the comprehension (generating list of lists) should look like this:

[[...generate one permutation...] \\ i <- [1..len], j <- [1..len-1], k 
<-[1..len-2] ... z <- [1..2]

But I don't know how to create a comprehension with variable number of 
generators or how to create a recursion inside the comprehension...

-- 
                                           Frantisek Fuka
(yes, that IS my real name)
(and it's pronounced "Fran-tjee-shek Foo-kah")
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