Can this haskell sample be shorter?

Question

This is my solution to exercise from YAHT: Exercise 4.6 Write a datatype Tuple which can hold one, two, three or four elements, depending on the constructor (that is, there should be four constructors, one for each number of arguments). Also provide functions tuple1 through tuple4 which take a tuple and return Just the value in that position, or Nothing if the number is in valid (i.e., you ask for the tuple4 on a tuple holding only two elements). When I wrote a first line I was excited about simplicity comparing to C# ``` data Tuplex a b c d = Tuple1 a | Tuple2 a b | Tuple3 a b c | Tuple4 a b c d -- class Tuplex { -- Tuplex(a p1){ _p1 = p1; } -- Tuplex(a p1, b p2){ _p1 = p1; _p2 = p2; } -- Tuplex(a p1, b p2, c p3){ _p1 = p1; _p2 = p2; _p3 = p3; } -- Tuplex(a p1, b p2, c p3, d p4){ _p1 = p1; _p2 = p2; _p3 = p3; _p4 = p4; } -- public Nullable _p1; -- public Nullable _p2; -- public Nullable _p3; -- public Nullable _p4; -- } ``` In C# I can access any field without pr…

Accepted Answer

I would try to keep it dead simple:

```
data Tuplex a b c d = Tuple1 a | Tuple2 a b | Tuple3 a b c | Tuple4 a b c d

toMaybes (Tuple1 p)       = (Just p, Nothing, Nothing, Nothing)
toMaybes (Tuple2 p q)     = (Just p, Just  q, Nothing, Nothing)
toMaybes (Tuple3 p q r)   = (Just p, Just  q, Just  r, Nothing)
toMaybes (Tuple4 p q r s) = (Just p, Just  q, Just  r, Just  s)

tuple1 t = p where (p,_,_,_) = toMaybes t 
tuple2 t = q where (_,q,_,_) = toMaybes t 
tuple3 t = r where (_,_,r,_) = toMaybes t 
tuple4 t = s where (_,_,_,s) = toMaybes t
```

Can this haskell sample be shorter?

Solution

Problem