Immutable means that once the constructor for an object has completed execution that instance can’t be altered. This is useful as it means you can pass references to the object around, without worrying that someone else is going to change its contents. Especially when dealing with concurrency, there are no locking issues with objects that … Read more
Structs are value types which means they are copied when they are passed around. So if you change a copy you are changing only that copy, not the original and not any other copies which might be around. If your struct is immutable then all automatic copies resulting from being passed by value will be … Read more
In general, methods that end in ! indicate that the method will modify the object it’s called on. Ruby calls these as “dangerous methods” because they change state that someone else might have a reference to. Here’s a simple example for strings: foo = “A STRING” # a string called foo foo.downcase! # modifies foo … Read more
Strings in Python are immutable (can’t be changed). Because of this, the effect of line.replace(…) is just to create a new string, rather than changing the old one. You need to rebind (assign) it to line in order to have that variable take the new value, with those characters removed. Also, the way you are … Read more