Versions of m

original.clj

(defn m
  "Measures the number of consonant sequences between
  the start of word and position j. If c is a consonant
  sequence and v a vowel sequence, and <...> indicates
  arbitrary presence,
    <c><v>       -> 0
    <c>vc<v>     -> 1
    <c>vcvc<v>   -> 2
    <c>vcvcvc<v> -> 3
    ...
  "
  [stemmer]
  (let [
        j (get-index stemmer)
        count-v (fn [n i]
                  (cond (> i j) [:return n i]
                        (vowel? stemmer i) [:break n i]
                        :else (recur n (inc i))))
        count-c (fn [n i]
                  (cond (> i j) [:return n i]
                        (consonant? stemmer i) [:break n i]
                        :else (recur n (inc i))))
        count-cluster (fn [n i]
                        (let [[stage1 n1 i1] (count-c n i)]
                          (if (= stage1 :return)
                            n1
                            (let [[stage2 n2 i2] (count-v (inc n1) (inc i1))]
                              (if (= stage2 :return)
                                n2
                                (recur n2 (inc i2)))))))
        [stage n i] (count-v 0 0)
        ]
    (if (= stage :return)
      n
      (count-cluster n (inc i)))))

suggestion.clj

(defn m
  "Measures the number of consonant sequences between
  the start of word and position j. If c is a consonant
  sequence and v a vowel sequence, and <...> indicates
  arbitrary presence,
    <c><v>       -> 0
    <c>vc<v>     -> 1
    <c>vcvc<v>   -> 2
    <c>vcvcvc<v> -> 3
    ...
  "
  ([stemmer]
    (m stemmer 0 0))
  
  ([stemmer num-c num-cs]
    (if (not (seq (:word stemmer))) ; Is the word empty? Then we reached the beginning of the stemmer
      (if (> num-c 1)               ; THEN1: More than 2 consonants in current counting?
        (inc num-cs)                ; THEN2: we have one more consonant sequence, and we return the number of sequences found plus 1
        num-cs)                     ; ELSE2: Return the number of sequences found
      (if (consonant? stemmer)                        ; ELSE1: Is there a consonant at the current index?
        (recur (pop-word stemmer) (inc num-c) num-cs) ; THEN3: increase the number of currently consecutice consonants, recur
        (if (> num-c 1)                               ; ELSE3: If not, check if we found more than 1 consecutive consonants
          (recur (pop-word stemmer) 0 (inc num-cs))   ; THEN4: If yes, we found one more sequence
          (recur (pop-word stemmer) 0 num-cs))))))    ; ELSE4: If not, then we found only one, and start anew

update.clj

(defn m
  "Measures the number of consonant sequences between the start of a word an
  position j. If c is a consonant sequence and v a vowel sequence, and <...>
  indicates arbitrary presence,
  <c><v>       -> 0
  <c>vc<v>     -> 1
  <c>vcvc<v>   -> 2
  <c>vcvcvc<v> -> 3
  ...
  "
  [stemmer]
  (let [consonant-group? (fn [ws] (consonant? (first ws)))]
    (->> stemmer
      (iterate pop-word)                    ; a sequence of all the parts of the word, from the whole word to the first letter.
      (take-while (fn [w] (seq (:word w)))) ; stop when done with the word
      (partition-by consonant?)             ; break it into vowel/consonant groups
      (reverse)                             ; reverse so the next step works
      (drop-while consonant-group?)         ; remove the first (was at the end of the sequence) constant group
      (filter consonant-group?)             ; filter out vowel groups
      count)))                              ; finally, count the remaining consonant groups