Using let inside ->> macro - clojure

Question

I have started learning clojure. I am stuck at using let inside ->> macro
The code is :
(defn make-summary [wordStr]
;// split string into words
(let [words (clojure.string/split wordStr #"[\[\]\(\),.\s+]")
;// convert words to lowercase.
lowerCaseWords (map clojure.string/lower-case words)]
;// remove stop words
(->> (remove-stop-words lowerCaseWords)
;// count the frequency of words
;// ---------- HERE IS THE PROBLEM ------------------------------
(let [totalWords (count )] ;// <--- HOW TO MAKE MACRO PUT THE THING HERE ???
(count-frequency)
;// sort on the basis of frequency
(sort #(> (get %1 1) (get %2 1)))
;// find the keywords
)
)))
I am stuck at the second let inside the defn function.
How can i code it ?

Answer 1

You can use your original code with the as-> threading macro added in clojure 1.5
instead of inserting its argument to the first (->) or to the last (->>) position of each form, it lets you specify the position:
(as-> [1 2 3] x
(conj x 4)
(map inc x)) ;=> '(2 3 4 5)
I think, the advice is to use -> or ->> when you can and only fall back to as-> if this is not easily done. The summarise function by #Thumbnail is a nice example of the readability you get with ->>.
You can think of as-> as a convenient shorthand for the following code:
(let [x [1 2 3]
x (conj x 4)
x (map inc x)] x)
Here is the relevant part of your code written with as->:
(as-> (remove-stop-words lowerCaseWords) x
(let [totalWords (count x)] .....

Answer 2

Following #DiegoBasch's advice ...
If you're looking for
the words in decreasing order of frequency of use
eliminating stop words and
exploiting the ->> macro
then the following might suit:
(defn summarise [text stop-words]
(->> text
(re-seq #"[a-zA-Z]+")
(map clojure.string/lower-case)
(remove stop-words)
frequencies
(sort-by (comp - val))
(map key)))
For examples
(summarise "Mary had a HUGE a lamb" #{})
("a" "mary" "had" "huge" "lamb")
(summarise "Mary had a HUGE a lamb" #{"huge"})
("a" "mary" "had" "lamb")
Notes
The function detects words as sequences of letters instead of
detecting specific separator characters. You can reverse this change
if you prefer.
I'd be inclined to make sure that the stop words too are lower case:
use (set (map clojure.string/lower-case stop-words)) instead of
stop-words in the remove. Otherwise stop words with upper case
letters will be ineffective.

Answer 3

It is not possible to have ->> insert the argument at any place other than last item of the form. But this can be used in a trick to make it happen :
(defn make-summary [wordStr]
;// split string into words
(let [words (clojure.string/split wordStr #"[\[\]\(\),.\s+]")
;// convert words to lowercase.
lowerCaseWords (map clojure.string/lower-case words)]
;// remove stop words
(->> (remove-stop-words lowerCaseWords)
;// count the frequency of words
(fn [LCW] (let [totalWords (count LCW)] ;// <--- HOW TO MAKE MACRO PUT THE THING HERE ???
(count-frequency)
;// sort on the basis of frequency
(sort #(> (get %1 1) (get %2 1)))
;// find the keywords
)
))))
What i have done is wrapped the things inside the function, and now you can put the argument at any place.