MergeSort + inversion counter, implemented in CoffeeScript

inversionCount.coffee

nums = [0,3,2,1,4,5,6,7,8,9]
inversions = [0]

mergeSort = (list,p,r,inver)->
        if p < r
                q = Math.floor((p + r) / 2)
                mergeSort(list,p,q,inver)
                mergeSort(list,q + 1,r,inver)
                merge(list,p,q,r,inver)

merge = (list,p,q,r,inver)->
        s1 = q - p
        s2 = r - q - 1
        L = []
        R = []
        for num in [0..s1]
                L[num] = list[p + num]
        for num in [0..s2]
                R[num] = list[q + num + 1]
        lc = 0
        rc = 0
        for num in [p..r]
                if lc < L.length && rc < R.length
                        if L[lc] <= R[rc]
                                list[num] = L[lc++]
                        else
                                list[num] = R[rc++]
                                if lc < L.length
                                        inver.push(L.length - lc)
                else if lc < L.length
                        list[num] = L[lc++]
                else if rc < R.length
                        list[num] = R[rc++]





mergeSort(nums,0,nums.length - 1, inversions)
console.log nums,inversions.reduce( (x,y)-> x + y ) 
# should provide the sorted list and 3 as the number of inversions