catala/tests/test_array/good/aggregation_3.catala_en

```catala
declaration scope S:
  output x content integer

scope S:
    definition x equals 0

# Map
    assertion (i + 2) for i among [1; 2; 3] = [3; 4; 5]

# Filter
    assertion (i among [1; 2; 3] such that i >= 2) = [2; 3]
    assertion ((i + 2) for i among [1; 2; 3] such that i > 2) = [5]

# Sum
    assertion sum integer of [1; 2; 3] = 6
    assertion sum integer of (i + 2) for i among [1; 2; 3] = 12

# Count
    assertion number of [1; 2; 3] = 3
    assertion (number of i among [1; 2; 3] such that i >= 2) = 2

# Extremum
    assertion maximum of [1; 2; 3] or if collection empty then 10 = 3
    assertion maximum of (decimal of i) for i among [1; 2; 3] or if collection empty then 10. = 3.

# Arg extremum
    assertion (i among [1; 2; 3]
                 such that decimal of ((2 - i) * (2 - i)) is minimum
                 or if collection empty then 42)
              = 2
```

```catala-test-inline
$ catala scopelang -s S
let scope S (x: integer|internal|output) =
  let x : integer = error_empty ⟨ ⟨true ⊢ 0⟩ | false ⊢ error_empty ∅ ⟩;
  assert (map (λ (i: integer) → i + 2) [ 1; 2; 3 ]) = [ 3; 4; 5 ];
  assert (filter (λ (i: integer) → i >= 2) [ 1; 2; 3 ]) = [ 2; 3 ];
  assert (map (λ (i: integer) → i + 2)
            filter (λ (i: integer) → i > 2) [ 1; 2; 3 ])
         = [ 5 ];
  assert (reduce
            (λ (sum1: integer) (sum2: integer) → sum1 + sum2)
            0
            [ 1; 2; 3 ])
         = 6;
  assert (reduce
            (λ (sum1: integer) (sum2: integer) → sum1 + sum2)
            0
            map (λ (i: integer) → i + 2) [ 1; 2; 3 ])
         = 12;
  assert (length [ 1; 2; 3 ]) = 3;
  assert (length filter (λ (i: integer) → i >= 2) [ 1; 2; 3 ]) = 2;
  assert (reduce
            (λ (max1: integer) (max2: integer) →
             if max1 > max2 then max1 else max2)
            10
            [ 1; 2; 3 ])
         = 3;
  assert (reduce
            (λ (max1: decimal) (max2: decimal) →
             if max1 > max2 then max1 else max2)
            10.
            map (λ (i: integer) → to_rat i) [ 1; 2; 3 ])
         = 3.;
  assert (reduce
            (λ (i_1: integer) (i_2: integer) →
             if
               (let i : integer = i_1 in
                to_rat ((2 - i) * (2 - i)))
               < let i : integer = i_2 in
                 to_rat ((2 - i) * (2 - i))
             then
               i_1
             else i_2)
            42
            [ 1; 2; 3 ])
         = 2
```

```catala-test-inline
$ catala interpret -s S
[RESULT] Computation successful! Results:
[RESULT] x = 0
```