Merge pull request #429 from yj-qin/array-filter

Add filter method to Array
moonbitlang · May 23, 2024 · 74ebec2 · 74ebec2
2 parents 8f150b8 + 4ec2ef3
commit 74ebec2
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diff --git a/array/array_test.mbt b/array/array_test.mbt
@@ -169,6 +169,11 @@ test "mapi_inplace" {
   inspect(e, content="[]")?
 }
 
+test "filter" {
+  let arr = [1, 2, 3, 4, 5, 6]
+  inspect(arr.filter(fn(x) { x % 2 == 0 }), content="[2, 4, 6]")?
+}
+
 test "is_empty" {
   let v = Array::new()
   @assertion.assert_true(v.is_empty())?

diff --git a/builtin/array.mbt b/builtin/array.mbt
@@ -407,6 +407,19 @@ pub fn mapi_inplace[T](self : Array[T], f : (Int, T) -> T) -> Unit {
   }
 }
 
+/// Filters the array with a predicate function.
+///
+/// # Example
+/// ```
+/// let arr = [1, 2, 3, 4, 5, 6]
+/// arr.filter(fn (x) { x % 2 == 0 }) // [2, 4, 6]
+/// ```
+pub fn filter[T](self : Array[T], f : (T) -> Bool) -> Array[T] {
+  let arr = []
+  self.iter(fn(e) { if f(e) { arr.push(e) } })
+  arr
+}
+
 /// Test if the vector is empty.
 ///
 /// # Example

diff --git a/builtin/builtin.mbti b/builtin/builtin.mbti
@@ -49,6 +49,7 @@ impl Array {
   extract_if[T](Self[T], (T) -> Bool) -> Self[T]
   fill[T](Self[T], T) -> Unit
   fill_with[T](Self[T], () -> T) -> Unit
+  filter[T](Self[T], (T) -> Bool) -> Self[T]
   flatten[T](Self[Self[T]]) -> Self[T]
   fold_left[T, U](Self[T], (U, T) -> U, ~init : U) -> U
   fold_lefti[T, U](Self[T], (Int, U, T) -> U, ~init : U) -> U