Add mutables.py.

I might regret this!

voussoirkit/mutables.py

@@ -0,0 +1,70 @@
+class Boolean:
+    def __init__(self, value):
+        self.set(value)
+
+    def __bool__(self):
+        return self.__value
+
+    def get(self):
+        return self.__value
+
+    def set(self, value):
+        if type(value) is not bool:
+            raise TypeError(value)
+
+        self.__value = value
+
+class Bytes:
+    def __init__(self, value):
+        self.set(value)
+
+    def get(self):
+        return self.__value
+
+    def set(self, value):
+        if type(value) is not bytes:
+            raise TypeError(value)
+
+        self.__value = value
+
+class Float:
+    def __init__(self, value):
+        self.set(value)
+
+    def get(self):
+        return self.__value
+
+    def set(self, value):
+        if type(value) not in (int, float):
+            raise TypeError(value)
+
+        self.__value = value
+
+class Integer:
+    def __init__(self, value):
+        self.set(value)
+
+    def get(self):
+        return self.__value
+
+    def set(self, value):
+        if type(value) is not int:
+            raise TypeError(value)
+
+        self.__value = value
+
+class String:
+    def __init__(self, value):
+        self.set(value)
+
+    def __str__(self):
+        return self.__value
+
+    def get(self):
+        return self.__value
+
+    def set(self, value):
+        if type(value) is not str:
+            raise TypeError(value)
+
+        self.__value = value