+ # Replace in `recv` the value of the attribute `mproperty` by `value`
+ fun write_attribute(mproperty: MAttribute, recv: Instance, value: Instance)
+ do
+ assert recv isa MutableInstance
+ recv.attributes[mproperty] = value
+ end
+
+ # Is the attribute `mproperty` initialized the instance `recv`?
+ fun isset_attribute(mproperty: MAttribute, recv: Instance): Bool
+ do
+ assert recv isa MutableInstance
+ return recv.attributes.has_key(mproperty)
+ end
+