ArrayView::join and FixedArray::join

array/array.mbti

@@ -47,6 +47,7 @@ impl FixedArray {
   from_array[T](Array[T]) -> Self[T]
   from_iter[T](Iter[T]) -> Self[T]
   is_sorted[T : Compare](Self[T]) -> Bool
+  join(Self[String], String) -> String
   last[A](Self[A]) -> A?
   makei[T](Int, (Int) -> T) -> Self[T]
   map[T, U](Self[T], (T) -> U) -> Self[U]
@@ -99,6 +100,7 @@ impl ArrayView {
   fold[A, B](Self[A], init~ : B, (B, A) -> B) -> B
   foldi[A, B](Self[A], init~ : B, (Int, B, A) -> B) -> B
   iter[A](Self[A]) -> Iter[A]
+  join(Self[String], String) -> String
   map[T, U](Self[T], (T) -> U) -> Array[U]
   map_inplace[T](Self[T], (T) -> T) -> Unit
   mapi[T, U](Self[T], (Int, T) -> U) -> Array[U]

array/fixedarray.mbt

@@ -1174,6 +1174,45 @@ pub fn FixedArray::last[A](self : FixedArray[A]) -> A? {
   }
 }
 
+///|
+/// Concatenate strings within an array into a single complete string.
+///
+/// Example:
+/// 
+/// ```moonbit
+/// test "FixedArray::join" {
+///   let fixed_array:FixedArray[String]=["1","2","3"]
+///   inspect!(fixed_array.join(","), content="1,2,3")
+/// }
+/// ```
+pub fn FixedArray::join(
+  self : FixedArray[String],
+  separator : @string.View
+) -> String {
+  let len = self.length()
+  if len == 0 {
+    return ""
+  }
+  let first = self[0]
+  let mut size_hint = first.length()
+  for i = 1; i < len; i = i + 1 {
+    size_hint += separator.length() + self[i].length()
+  }
+  let string = StringBuilder::new(size_hint~)
+  if separator.is_empty() {
+    for i = 0; i < len; i = i + 1 {
+      string.write_string(self[i])
+    }
+  } else {
+    string.write_string(self[0])
+    for i = 1; i < len; i = i + 1 {
+      string.write_string(separator.to_string())
+      string.write_string(self[i])
+    }
+  }
+  string.to_string()
+}
+
 ///|
 test "FixedArray::last/empty" {
   let empty : FixedArray[Int] = []

array/view.mbt

@@ -365,6 +365,23 @@ pub fn View::to_array[T](self : View[T]) -> Array[T] {
   }
 }
 
+///|
+/// Concatenate strings within an array into a single complete string.
+///
+/// Example:
+///
+/// ```moonbit
+/// test "View::join" {
+///   let a:Array[String]=["1","2","3"]
+///   let array_view = a[:]
+///   inspect!(array_view.join(","), content="1,2,3")
+/// }
+/// ```
+pub fn View::join(self : ArrayView[String], separator : String) -> String {
+  let array = self.to_array()
+  @string.concat(array, separator~)
+}
+
 ///|
 pub impl[X : Show] Show for View[X] with output(self, logger) {
   logger.write_iter(self.iter())