Partition a list into sublists of length n in various languages.

partition.hs

-- | The 'partition' function splits a list into sublists of length n.
partition :: Int -> [a] -> [[a]]
partition n = unfoldr step
  where
    step :: [a] -> Maybe ([a], [a])
    step [] = Nothing
    step xs = Just (take n xs, drop n xs)

partition.js

// Partition a list into sublists of length n.
function partition(n, list) {
    return list.reduce(function(acc, item) {
        var current = acc[acc.length - 1];
        
        if (current.length === n) {
            current = [];
            acc.push(current);
        }
        
        current.push(item);
        return acc;
    }, [[]]);
}

partition.py

def partition(n, list):
    """Partition a list into sublists of length n."""
    def step(acc, item):
        current = acc[-1]
        
        if len(current) == n:
            current = []
            acc.append(current)
        
        current.append(item)
        return acc
    
    return reduce(step, list, [[]])

partition.rb

# Partition a list into sublists of length n.
def partition(n, list)
  list.inject([[]]) {|acc, item|
    current = acc.last
    
    if current.length == n
      current = []
      acc << current
    end
    
    current << item
    acc
  }
end