How does IPL find the value of a variable?
In IPL variable values are stored in a environment. An environment is a set of name/value pairs. Environments can be nested. A new nested environment is created when: • Entering a block statement (a list of statements between { and }). • Executing a method call. • Executing a for statement. A nested environment keeps a reference to its parent (the environment in which it was created). Environments are statically scoped, this means that the parent environment is defined by its “location” in the source code. IPL first looks for a variable in the current environment, if the variable isn’t there IPL looks for it (recursively) in the parent environment. If there isn’t a variable with that name in any of the scoped environments, IPL creates it in the current environment.
