Question

    n = (count somevector)        
   (foo [w] ( for [i (range n) 
                   j (range w)
                   :let [n (* i j)] 
                   :while ( < i j)
                  ] 
              (println n)))

When i run it.

=> (foo 10)
ClassCastException clojure.lang.LazySeq cannot be cast to clojure.lang.IFn HelloWorld.core/foo

What I am really looking to do is have a couple of nested for loops and have some ifs and else inside it do some checking.

Edit ::

As it turns out the following also causes error

(defn foo [arg]
 (      
      for [ i (range (count vector)) ]
      (
        for [j arg ]
        [i j]
        ) 

     ) ) 

IllegalArgumentException Don’t know how to create ISeq from: java.lang.Long clojure.lang.RT.seqFrom

Edit::

the following works

(defn foo [arg]
  (def w arg) 
(for [ i (range (count vector)) ]
      (
        for [j (range v)  ]
        [i j]
        )
  )   )

Now can someone help me understand why would it not work in the first place ?

Answer 1

Don’t know how to create ISeq from: java.lang.Long clojure.lang.RT.seqFrom

This error message states the cause of exception accurately.
I guess you passed a long value where a seq is expected.
I could reproduce it:

user> (def v [1 2 3])
#'user/v
user> (defn foo [arg]
        (for [ i (range (count v)) ]
             (for [j arg ]
                  [i j]))) 
#'user/foo
user> (foo (range 3))
(([0 0] [0 1] [0 2]) ([1 0] [1 1] [1 2]) ([2 0] [2 1] [2 2]))
user> (foo 3)
; Evaluation aborted.
; Don't know how to create ISeq from: java.lang.Long
;  [Thrown class java.lang.IllegalArgumentException]

Your foo function works. However, the arg argument must be a seq,
because arg is binded in the nested for to j