haskell - Stuck in recursion in rangeProduct function -

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I am starting in Haskell and I am stuck in a simple recurrence function.

I'm trying to define a function range for the product that is given when natural number is given and n product

m * (m + 1) ... (n-1) * n

should return the function when n is smaller than meter

Whatever I have tried: 

  rangeProduct :: int - & gt; Int - & gt; Int Range Product m n | M & gt; N = 0 | Otherwise = M * N * Category Product (M + 1) (N-1)

But this is incorrect because in another protector, when the meter grows up and at some point , Will get bigger than zero and it will get zero, which is how much it has done to multiply zero, resulting in the function of 0 every time I will run.

I know the answer is simple but I'm stuck. Can anyone help? Thanks!

Why is the growth and decrease at the same time? Just go in one direction: 

  Category Product m n | M & gt; N = 0 | I == N = N | Otherwise = M * Category Product (M + 1) n

Although you can not easily define it 

  rangeProduct :: Integer - & gt; ; Integer - & gt; Integer category product m n | | M & gt; N = 0 | Otherwise = product [m ... n]

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