fix: @= and @@= returned numbers instead of strings when working with strings/list of strings

Author: SuperFola

docs/arkdoc/List.txt

@@ -179,3 +179,24 @@
 * (print lst)  # ["x" "y" "z" "g" "f"]
 * =end
 #--
+
+--#
+* @name @@=
+* @brief Set an element in a list of lists or list of strings, in place
+* @details Return the newly added element
+* @param lst list
+* @param y index (can be negative to start from the end)
+* @param x index (can be negative to start from the end)
+* @param value anything (for list of lists) or string (for list of strings)
+* =begin
+* (mut lst [[1 2 3] [4 5 6] [7 8 9]])
+* (print (@@= lst 0 1 "x"))  # x
+* (print (@@= lst -1 1 "y"))  # y
+* (print (@@= lst 0 -1 "z"))  # z
+* (mut lst2 ["abc" "def" "ghi"])
+* (print (@@= lst2 0 1 "0"))  # 0
+* (print (@@= lst2 -1 1 "1"))  # 1
+* (print (@@= lst2 0 -1 "2"))  # 2
+* (print lst2)  # [a02 def g1i]
+* =end
+#--

lib/std

@@ -970,7 +970,7 @@ namespace Ark
                             {
                                 list->stringRef()[static_cast<std::size_t>(idx)] = new_value.string()[0];
                                 if (arg)
-                                    push(Value(new_value.string()[0]), context);
+                                    push(Value(std::string(1, new_value.string()[0])), context);
                             }
                         }
                         DISPATCH();
@@ -1040,7 +1040,7 @@ namespace Ark
                             {
                                 list->list()[static_cast<std::size_t>(idx_y)].stringRef()[static_cast<std::size_t>(idx_x)] = new_value.string()[0];
                                 if (arg)
-                                    push(Value(new_value.string()[0]), context);
+                                    push(Value(std::string(1, new_value.string()[0])), context);
                             }
                         }
                         DISPATCH();

src/arkreactor/VM/VM.cpp

@@ -108,15 +108,26 @@
         (test:eq (@= numbers 2 5) 5)
         (test:eq (@= numbers -1 9) 9)
         (@= numbers -2 8)
-        (test:eq numbers [0 1 5 8 9] "@=") })
+        (test:eq numbers [0 1 5 8 9] "@=")
+
+        (mut strings "abcdef")
+        (test:eq (@= strings 2 "0") "0")
+        (test:eq (@= strings -1 "1") "1")
+        (test:eq strings "ab0de1") })
 
     (test:case "in place 2D mutation with @@=" {
         (mut numbers [[0 1 2 3] [4 5 6 7] [8 9 0 1]])
         (test:eq (@@= numbers 0 0 9) 9)
         (test:eq (@@= numbers 1 1 "a") "a")
         (@@= numbers -1 -1 -1)
         (@@= numbers -2 -2 -2)
-        (test:eq numbers [[9 1 2 3] [4 "a" -2 7] [8 9 0 -1]]) })
+        (test:eq numbers [[9 1 2 3] [4 "a" -2 7] [8 9 0 -1]])
+
+        (mut strings ["abc" "def" "ghi"])
+        (test:eq (@@= strings 0 1 "0") "0")
+        (test:eq (@@= strings -1 1 "1") "1")
+        (test:eq (@@= strings 0 -1 "2") "2")
+        (test:eq strings ["a02" "def" "g1i"]) })
 
     (test:case "in place list mutation" {
         (mut c a)