feat: add Array.repeat

crates/erg_compiler/context/initialize/classes.rs

@@ -1603,7 +1603,7 @@ impl Context {
             2,
         );
         array_add.register_builtin_erg_impl(OP_ADD, t, Immutable, Visibility::BUILTIN_PUBLIC);
-        let out_t = array_t(T.clone(), N.clone() + M);
+        let out_t = array_t(T.clone(), N.clone() + M.clone());
         array_add.register_builtin_const(
             OUTPUT,
             Visibility::BUILTIN_PUBLIC,
@@ -1619,6 +1619,19 @@ impl Context {
         )
         .quantify();
         array_.register_builtin_erg_impl(FUNC_PUSH, t, Immutable, Visibility::BUILTIN_PUBLIC);
+        let repeat_t = no_var_fn_met(
+            arr_t.clone(),
+            vec![pos(singleton(Nat, M.clone()))],
+            vec![],
+            array_t(T.clone(), N.clone() * M.clone()),
+        )
+        .quantify();
+        array_.register_builtin_erg_impl(
+            FUNC_REPEAT,
+            repeat_t,
+            Immutable,
+            Visibility::BUILTIN_PUBLIC,
+        );
         // [T; N].MutType! = [T; !N] (neither [T!; N] nor [T; N]!)
         let mut_type =
             ValueObj::builtin_class(poly(MUT_ARRAY, vec![TyParam::t(T.clone()), N.clone()]));

crates/erg_compiler/context/initialize/mod.rs

@@ -243,6 +243,7 @@ const FUNC_DEDUP: &str = "dedup";
 const FUNC_CONCAT: &str = "concat";
 const FUNC_DIFF: &str = "diff";
 const FUNC_PUSH: &str = "push";
+const FUNC_REPEAT: &str = "repeat";
 const PROC_PUSH: &str = "push!";
 const FUNC_MERGE: &str = "merge";
 const PROC_MERGE: &str = "merge!";

crates/erg_compiler/lib/core/_erg_array.py

@@ -127,6 +127,13 @@ class Array(list):
             self.remove(item)
         return self
 
+    def repeat(self, n):
+        from copy import deepcopy
+        new = []
+        for _ in range(n):
+            new.extend(deepcopy(self))
+        return Array(new)
+
 class UnsizedArray:
     elem: object
     def __init__(self, elem):

tests/should_ok/array.er

@@ -33,3 +33,8 @@ assert l == [4, 3]
 
 l.clear!()
 assert l == []
+
+l2 = [![1]].repeat 3
+l2[0].push! 2
+ans: Array(Array(Nat)) = [[1, 2], [1], [1]]
+assert l2 == ans