Add `windows` method to array (#4136)

Co-authored-by: Laurenz <laurmaedje@gmail.com>

2 files changed, 36 insertions, 1 deletions

diff --git a/crates/typst/src/foundations/array.rs b/crates/typst/src/foundations/array.rs
index 123dc1f5..2f65800e 100644
--- a/crates/typst/src/foundations/array.rs
+++ b/crates/typst/src/foundations/array.rs
@@ -790,6 +790,26 @@ impl Array {
         }
     }
 
+    /// Returns sliding windows of `window-size` elements over an array.
+    ///
+    /// If the array length is less than `window-size`, this will return an empty array.
+    ///
+    /// ```example
+    /// #let array = (1, 2, 3, 4, 5, 6, 7, 8)
+    /// #array.windows(5)
+    /// ```
+    #[func]
+    pub fn windows(
+        self,
+        /// How many elements each window will contain.
+        window_size: NonZeroUsize,
+    ) -> Array {
+        self.0
+            .windows(window_size.get())
+            .map(|window| Array::from(window).into_value())
+            .collect()
+    }
+
     /// Return a sorted version of this array, optionally by a given key
     /// function. The sorting algorithm used is stable.
     ///
diff --git a/tests/suite/foundations/array.typ b/tests/suite/foundations/array.typ
index 24dad1c1..1df83fc6 100644
--- a/tests/suite/foundations/array.typ
+++ b/tests/suite/foundations/array.typ
@@ -328,6 +328,21 @@
 // Error: 19-21 number must be positive
 #(1, 2, 3).chunks(-5)
 
+--- array-windows ---
+// Test the `windows` method.
+#test(().windows(5), ())
+#test((1, 2, 3).windows(5), ())
+#test((1, 2, 3, 4, 5).windows(3), ((1, 2, 3), (2, 3, 4), (3, 4, 5)))
+#test((1, 2, 3, 4, 5, 6, 7, 8).windows(5), ((1, 2, 3, 4, 5), (2, 3, 4, 5, 6), (3, 4, 5, 6, 7), (4, 5, 6, 7, 8)))
+
+--- array-windows-size-zero ---
+// Error: 20-21 number must be positive
+#(1, 2, 3).windows(0)
+
+--- array-windows-size-negative ---
+// Error: 20-22 number must be positive
+#(1, 2, 3).windows(-5)
+
 --- array-sorted ---
 // Test the `sorted` method.
 #test(().sorted(), ())
@@ -514,4 +529,4 @@
 
 --- array-reduce-unexpected-argument ---
 // Error: 19-21 unexpected argument
-#(1, 2, 3).reduce(() => none) 
\ No newline at end of file
+#(1, 2, 3).reduce(() => none)