I'm trying to take a list of lists of tuple and turn each list of tuples into a single tuple. Like this:

Currently have: 

```
[[("Erikson,Ann",2.0,3),("Erikson,Ann",3.33,3)],[("Lewis,Buck",2.66,1), 
  ("Lewis,Buck",2.0,3)],[("Smith,John",0.0,1),("Smith,John",1.66,3), 
  ("Smith,John",1.33,3)],[("Torvell,Sarah",4.0,3)]]

```

And I want the form to be a single list of tuples. One tuple for each persons name. 
Along with combining the list of tuples into a single tuple I want to use the second and third elements of each tuple to calculate the gpa of the person. The second number is the grade point for that class and the third number is the credits for the class.
What I need to do is take the sum of credits \* gradepoint for each tuple and then divide that sum by the sum of all the credits in each tuple. 

What i have so far, that doesn't work is this...

```
     calcGPA :: MyType2 -> MyType2 -> (String, Double, Double)
     calcGPA (a,b,c) (d,e,f) = (a, ((b*(fromIntegral c))+(e*(fromIntegral 
     f))/(b+e)), 
     (b+e))

```

Where i am passing in the first list of lists I show at the top of this post.

Am I going in the right direction to solve this problem. Any tips or help would be appreciated.

Thank you

---

EDIT

Thank you for the help! Helped me understand what was actually going on. I wrote the cumulativeSums fuction as follow:

```
     cumulativeSums :: (Double, Int) -> (String, Double, Int) -> (Double, 
     Int)
     cumulativeSums (a,b) (c,d,e) = (a+(d*e), b+e)

```

I'm confused on the chunk of code you have above with the let. Where does this go? Do I put it in its own function that I call passing in the list of list of tuples?

Thank you

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_Now that im trying to output credits also

```
    calcGPA :: [(String, Double, Int)] -> (String, Double, Int)
    calcGPA grades = let name                        = (\ (name, _, _) -> 
    name) (head grades)
                         (name, weightedSum, sumOfWeights) = foldl 
    cumulativeSums (name, 0, 0) grades
                 gpa                         = weightedSum / sumOfWeights
                     in  (name, gpa, credits)

```