Quicksort in Haskell, Python, CoffeeScript and C

qa.coffee

qs = (arr) ->
  if arr.length <= 1
    return arr
  [].concat qs(i for i in arr when i < arr[0]), [arr[0]], qs(i for i in arr when i > arr[0])

qa2.hs

qsort (p:xs) = qsort [x | x<-xs, x<p] ++ [p] ++ qsort [x | x<-xs, x>=p]

qs.c

// To sort array a[] of size n: qsort(a,0,n-1)

void qsort(int a[], int lo, int hi) 
{
  int h, l, p, t;

  if (lo < hi) {
    l = lo;
    h = hi;
    p = a[hi];

    do {
      while ((l < h) && (a[l] <= p)) 
          l = l+1;
      while ((h > l) && (a[h] >= p))
          h = h-1;
      if (l < h) {
          t = a[l];
          a[l] = a[h];
          a[h] = t;
      }
    } while (l < h);

    a[hi] = a[l];
    a[l] = p;

    qsort( a, lo, l-1 );
    qsort( a, l+1, hi );
  }
}

qs.py

def qs(array):
    if len(array) == 0 or len(array) == 1:
        return array

    p = array[0]

    lesser = [i for i in array if i < p]
    greater = [i for i in array if i > p]

    return qs(lesser) + [p] + qs(greater)

# Or even


def qs(ar):
    if len(ar) == 0 or len(ar) == 1:
        return ar

    p = ar[0]
    return qs([i for i in ar if i < p]) + [p] + qs([i for i in ar if i > p])

quicksort.hs

quicksort :: Ord a => [a] -> [a]
quicksort []     = []
quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater)
    where
        lesser  = filter (< p) xs
        greater = filter (>= p) xs