Add inc!, dec! to Int

compiler/erg_compiler/lib/std/_erg_str.py

@@ -13,27 +13,47 @@ class Str(str):
             return Str(self[i])
         else:
             return None
+    def mutate(self):
+        return StrMut(self)
 
-class StrMut(Str):
+class StrMut(): # Inherits Str
+    value: Str
+
+    def __init__(self, s: str):
+        self.value = s
+    def __repr__(self):
+        return self.value.__repr__()
+    def __eq__(self, other):
+        if isinstance(other, Str):
+            return self.value == other
+        else:
+            return self.value == other.value
+    def __ne__(self, other):
+        if isinstance(other, Str):
+            return self.value != other
+        else:
+            return self.value != other.value
     def try_new(s: str):
         if isinstance(s, str):
-            return StrMut(s)
+            self = StrMut()
+            self.value = s
+            return self
         else:
             return Error("Str! can't be other than str")
     def clear(self):
-        self = ""
+        self.value = ""
     def pop(self):
-        if len(self) > 0:
-            last = self[-1]
-            self = self[:-1]
+        if len(self.value) > 0:
+            last = self.value[-1]
+            self.value = self.value[:-1]
             return last
         else:
             return Error("Can't pop from empty `Str!`")
     def push(self, c: str):
-        self += c
+        self.value += c
     def remove(self, idx: int):
-        char = self[idx]
-        self = self[:idx] + self[idx+1:]
+        char = self.value[idx]
+        self.value = self.value[:idx] + self.value[idx+1:]
         return char
     def insert(self, idx: int, c: str):
-        self = self[:idx] + c + self[idx:]
+        self.value = self.value[:idx] + c + self.value[idx:]