feat: array concat method (#7199)

Co-authored-by: Tom French <15848336+TomAFrench@users.noreply.github.com>
Co-authored-by: Ary Borenszweig <asterite@gmail.com>

cspell.json

@@ -60,6 +60,7 @@
         "combinators",
         "compinit",
         "comptime",
+        "concat",
         "cpus",
         "cranelift",
         "critesjosh",

docs/docs/noir/concepts/data_types/arrays.md

@@ -255,6 +255,23 @@ fn main() {
 }
 ```
 
+### concat
+
+Concatenates this array with another array.
+
+```rust
+fn concat<let M: u32>(self, array2: [T; M]) -> [T; N + M]
+```
+
+```rust
+fn main() {
+    let arr1 = [1, 2, 3, 4];
+    let arr2 = [6, 7, 8, 9, 10, 11];
+    let concatenated_arr = arr1.concat(arr2);
+    assert(concatenated_arr == [1, 2, 3, 4, 6, 7, 8, 9, 10, 11]);
+}
+```
+
 ### as_str_unchecked
 
 Converts a byte array of type `[u8; N]` to a string. Note that this performs no UTF-8 validation -

noir_stdlib/src/array/mod.nr

@@ -136,6 +136,29 @@ impl<T, let N: u32> [T; N] {
         }
         ret
     }
+
+    /// Concatenates this array with another array.
+    ///
+    /// Example:
+    ///
+    /// ```noir
+    /// fn main() {
+    ///     let arr1 = [1, 2, 3, 4];
+    ///     let arr2 = [6, 7, 8, 9, 10, 11];
+    ///     let concatenated_arr = arr1.concat(arr2);
+    ///     assert(concatenated_arr == [1, 2, 3, 4, 6, 7, 8, 9, 10, 11]);
+    /// }
+    /// ```
+    pub fn concat<let M: u32>(self, array2: [T; M]) -> [T; N + M] {
+        let mut result = [crate::mem::zeroed(); N + M];
+        for i in 0..N {
+            result[i] = self[i];
+        }
+        for i in 0..M {
+            result[i + N] = array2[i];
+        }
+        result
+    }
 }
 
 impl<T, let N: u32> [T; N]
@@ -232,4 +255,36 @@ mod test {
     fn map_empty() {
         assert_eq([].map(|x| x + 1), []);
     }
+
+    #[test]
+    fn concat() {
+        let arr1 = [1, 2, 3, 4];
+        let arr2 = [6, 7, 8, 9, 10, 11];
+        let concatenated_arr = arr1.concat(arr2);
+        assert_eq(concatenated_arr, [1, 2, 3, 4, 6, 7, 8, 9, 10, 11]);
+    }
+
+    #[test]
+    fn concat_zero_length_with_something() {
+        let arr1 = [];
+        let arr2 = [1];
+        let concatenated_arr = arr1.concat(arr2);
+        assert_eq(concatenated_arr, [1]);
+    }
+
+    #[test]
+    fn concat_something_with_zero_length() {
+        let arr1 = [1];
+        let arr2 = [];
+        let concatenated_arr = arr1.concat(arr2);
+        assert_eq(concatenated_arr, [1]);
+    }
+
+    #[test]
+    fn concat_zero_lengths() {
+        let arr1: [Field; 0] = [];
+        let arr2: [Field; 0] = [];
+        let concatenated_arr = arr1.concat(arr2);
+        assert_eq(concatenated_arr, []);
+    }
 }