10th November
Error Handling
Error handling is quite similar to how return statements were handled. If you think
about it, when a return statement is encountered, evaluation stops and returns the value
that has been evaluated from the statements till that point. Encountering an error
is not very different. When an error is encountered you stop evaluation and return
the value, just that in this case it's a object of type error. Instead of boolean
or integer etc.
Kinda like how go handles errors, it's just a value. It's a polarizing topic, but I like
that an error is just a value and you can decide what you want to do with it.
Commit:b981295 (opens in a new tab)
Binding Identifiers & Enviornment
Currently, the evaluator does not know what to do when a let statement is encountered, or for that matter what to do when an identifier is come across, either.
To be able to handle identifiers we need to store the values assosiated with them and
be able to get these values later on. So we define an Enviornment, that wraps a Hash
map that allows us to store and retreieve identifiers. It only needs two methods and is
a struct. This should make it easier to define scope for an indentifier. This will be
handled later when we deal with functions and calls.
Once this was in place, the evaluator was updated to accept an enviornment variable. That's it.o