Pascal's Triangle - Remove hack












2












$begingroup$


I had a thought last night on how I could easily write a Pascal's Triangle generator basically just using partition and map. I tried writing it this morning, and it got slightly more complicated than I originally thought it would, although it's still pretty nice.



My main concern is the wrap "hack" that I'm using. I found two similar, but different ways of writing it. I can either wrap the input to the iteration function in 0s, or I can wrap the result of the iteration function in 1s. Both give the same result, but the need for a wrapping helper pollutes an otherwise nice ->> chain. If anyone can think of how I can avoid a separate anonymous function here, and ideally avoid wrapping the input/output in 0s/1s, I'd appreciate it. I'll take any other critique as well, although there isn't much else going on here.



Usage:



(let [pre-t (pascals-triangle-pre) ; Wrapping pre-processing

      post-t (pascals-triangle-post) ; Wrapping post-processing

      n 5]

  (println (take n pre-t))

  (println (take n post-t)))



([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])

([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])





(ns minesweeper.irrelevant.pas-tri)



(defn pascals-triangle-post 

  (let [wrap #(vec (concat [1] % [1]))]

    (iterate #(->> %

                   (partition 2 1)

                   (mapv (partial apply +'))

                   (wrap))

             [1])))



(defn pascals-triangle-pre 

  (let [wrap #(vec (concat [0] % [0]))]

    (iterate #(->> %

                   (wrap)

                   (partition 2 1)

                   (mapv (partial apply +')))

             [1])))





clojure







share|improve this question









$endgroup$

















    2












    $begingroup$


    I had a thought last night on how I could easily write a Pascal's Triangle generator basically just using partition and map. I tried writing it this morning, and it got slightly more complicated than I originally thought it would, although it's still pretty nice.



    My main concern is the wrap "hack" that I'm using. I found two similar, but different ways of writing it. I can either wrap the input to the iteration function in 0s, or I can wrap the result of the iteration function in 1s. Both give the same result, but the need for a wrapping helper pollutes an otherwise nice ->> chain. If anyone can think of how I can avoid a separate anonymous function here, and ideally avoid wrapping the input/output in 0s/1s, I'd appreciate it. I'll take any other critique as well, although there isn't much else going on here.



    Usage:



    (let [pre-t (pascals-triangle-pre) ; Wrapping pre-processing
    
      post-t (pascals-triangle-post) ; Wrapping post-processing
    
      n 5]
    
  (println (take n pre-t))
    
  (println (take n post-t)))
    

    
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])
    
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])
    




    (ns minesweeper.irrelevant.pas-tri)
    

    
(defn pascals-triangle-post 
    
  (let [wrap #(vec (concat [1] % [1]))]
    
    (iterate #(->> %
    
                   (partition 2 1)
    
                   (mapv (partial apply +'))
    
                   (wrap))
    
             [1])))
    

    
(defn pascals-triangle-pre 
    
  (let [wrap #(vec (concat [0] % [0]))]
    
    (iterate #(->> %
    
                   (wrap)
    
                   (partition 2 1)
    
                   (mapv (partial apply +')))
    
             [1])))





    clojure







    share|improve this question









    $endgroup$















      2












      2








      2





      $begingroup$


      I had a thought last night on how I could easily write a Pascal's Triangle generator basically just using partition and map. I tried writing it this morning, and it got slightly more complicated than I originally thought it would, although it's still pretty nice.



      My main concern is the wrap "hack" that I'm using. I found two similar, but different ways of writing it. I can either wrap the input to the iteration function in 0s, or I can wrap the result of the iteration function in 1s. Both give the same result, but the need for a wrapping helper pollutes an otherwise nice ->> chain. If anyone can think of how I can avoid a separate anonymous function here, and ideally avoid wrapping the input/output in 0s/1s, I'd appreciate it. I'll take any other critique as well, although there isn't much else going on here.



      Usage:



      (let [pre-t (pascals-triangle-pre) ; Wrapping pre-processing
      
      post-t (pascals-triangle-post) ; Wrapping post-processing
      
      n 5]
      
  (println (take n pre-t))
      
  (println (take n post-t)))
      

      
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])
      
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])
      




      (ns minesweeper.irrelevant.pas-tri)
      

      
(defn pascals-triangle-post 
      
  (let [wrap #(vec (concat [1] % [1]))]
      
    (iterate #(->> %
      
                   (partition 2 1)
      
                   (mapv (partial apply +'))
      
                   (wrap))
      
             [1])))
      

      
(defn pascals-triangle-pre 
      
  (let [wrap #(vec (concat [0] % [0]))]
      
    (iterate #(->> %
      
                   (wrap)
      
                   (partition 2 1)
      
                   (mapv (partial apply +')))
      
             [1])))





      clojure







      share|improve this question









      $endgroup$




      I had a thought last night on how I could easily write a Pascal's Triangle generator basically just using partition and map. I tried writing it this morning, and it got slightly more complicated than I originally thought it would, although it's still pretty nice.



      My main concern is the wrap "hack" that I'm using. I found two similar, but different ways of writing it. I can either wrap the input to the iteration function in 0s, or I can wrap the result of the iteration function in 1s. Both give the same result, but the need for a wrapping helper pollutes an otherwise nice ->> chain. If anyone can think of how I can avoid a separate anonymous function here, and ideally avoid wrapping the input/output in 0s/1s, I'd appreciate it. I'll take any other critique as well, although there isn't much else going on here.



      Usage:



      (let [pre-t (pascals-triangle-pre) ; Wrapping pre-processing
      
      post-t (pascals-triangle-post) ; Wrapping post-processing
      
      n 5]
      
  (println (take n pre-t))
      
  (println (take n post-t)))
      

      
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])
      
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])
      




      (ns minesweeper.irrelevant.pas-tri)
      

      
(defn pascals-triangle-post 
      
  (let [wrap #(vec (concat [1] % [1]))]
      
    (iterate #(->> %
      
                   (partition 2 1)
      
                   (mapv (partial apply +'))
      
                   (wrap))
      
             [1])))
      

      
(defn pascals-triangle-pre 
      
  (let [wrap #(vec (concat [0] % [0]))]
      
    (iterate #(->> %
      
                   (wrap)
      
                   (partition 2 1)
      
                   (mapv (partial apply +')))
      
             [1])))





      clojure




      clojure






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked May 14 '18 at 16:14









      CarcigenicateCarcigenicate

      2,85511229




      2,85511229






















          1 Answer
          1






          active

          oldest

          votes


















          1












          $begingroup$

          There's a simpler way.



          To get the next line




          • take two copies of the line,

          • extend them respectively with 0 at the start and with 0 at the end, and

          • add the corresponding elements.


          In Clojure, 



          (defn pascal 
          
  (iterate
          
    #(mapv + (cons 0 %) (conj % 0))
          
    [1]))
          

          
=> (take 5 (pascal))
          
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])


          This avoids the partitioning.




          Not sure if it's what you're looking for, but showing off was irresistible.






          share|improve this answer









          $endgroup$













          • $begingroup$
            Cool, thanks. Can't complain half a year later.
            $endgroup$
            – Carcigenicate
            6 hours ago











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          1 Answer
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          active

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1












          $begingroup$

          There's a simpler way.



          To get the next line




          • take two copies of the line,

          • extend them respectively with 0 at the start and with 0 at the end, and

          • add the corresponding elements.


          In Clojure, 



          (defn pascal 
          
  (iterate
          
    #(mapv + (cons 0 %) (conj % 0))
          
    [1]))
          

          
=> (take 5 (pascal))
          
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])


          This avoids the partitioning.




          Not sure if it's what you're looking for, but showing off was irresistible.






          share|improve this answer









          $endgroup$













          • $begingroup$
            Cool, thanks. Can't complain half a year later.
            $endgroup$
            – Carcigenicate
            6 hours ago
















          1












          $begingroup$

          There's a simpler way.



          To get the next line




          • take two copies of the line,

          • extend them respectively with 0 at the start and with 0 at the end, and

          • add the corresponding elements.


          In Clojure, 



          (defn pascal 
          
  (iterate
          
    #(mapv + (cons 0 %) (conj % 0))
          
    [1]))
          

          
=> (take 5 (pascal))
          
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])


          This avoids the partitioning.




          Not sure if it's what you're looking for, but showing off was irresistible.






          share|improve this answer









          $endgroup$













          • $begingroup$
            Cool, thanks. Can't complain half a year later.
            $endgroup$
            – Carcigenicate
            6 hours ago














          1












          1








          1





          $begingroup$

          There's a simpler way.



          To get the next line




          • take two copies of the line,

          • extend them respectively with 0 at the start and with 0 at the end, and

          • add the corresponding elements.


          In Clojure, 



          (defn pascal 
          
  (iterate
          
    #(mapv + (cons 0 %) (conj % 0))
          
    [1]))
          

          
=> (take 5 (pascal))
          
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])


          This avoids the partitioning.




          Not sure if it's what you're looking for, but showing off was irresistible.






          share|improve this answer









          $endgroup$



          There's a simpler way.



          To get the next line




          • take two copies of the line,

          • extend them respectively with 0 at the start and with 0 at the end, and

          • add the corresponding elements.


          In Clojure, 



          (defn pascal 
          
  (iterate
          
    #(mapv + (cons 0 %) (conj % 0))
          
    [1]))
          

          
=> (take 5 (pascal))
          
([1] [1 1] [1 2 1] [1 3 3 1] [1 4 6 4 1])


          This avoids the partitioning.




          Not sure if it's what you're looking for, but showing off was irresistible.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 6 hours ago









          ThumbnailThumbnail

          1,30157




          1,30157












          • $begingroup$
            Cool, thanks. Can't complain half a year later.
            $endgroup$
            – Carcigenicate
            6 hours ago


















          • $begingroup$
            Cool, thanks. Can't complain half a year later.
            $endgroup$
            – Carcigenicate
            6 hours ago
















          $begingroup$
          Cool, thanks. Can't complain half a year later.
          $endgroup$
          – Carcigenicate
          6 hours ago




          $begingroup$
          Cool, thanks. Can't complain half a year later.
          $endgroup$
          – Carcigenicate
          6 hours ago


















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