I think Associative Array should throw Exception
Jesse.K.Phillips+D at gmail.com
Tue Sep 1 18:20:17 UTC 2020
This is going to be a hard one for me to argue but I'm going to
give it a try.
Today if you attempt to access a key from an associative array
(AA) that does not exist inside the array, a RangeError is
thrown. This is similar to when an array is accessed outside the
dict["Hello"] // RangeError
arr // RangeError
There are many things written on the difference between
Exception and Error.
* Errors are for programming bugs and Exceptions are environmental
* Exceptions can be caught, Errors shouldn't be (stack may not
* Exceptions are recoverable, Errors aren't recoverable
* Errors can live in nothrow, Exceptions can't
* Always verify input
I don't have an issue with the normal array RangeError, there is
a clear means for claiming your access is a programming bug.
However associative arrays tend to have both the key and value as
Trying to create a contract for any given method to validate the
AA as input becomes cumbersome. I would say it is analogous to
`find` throwing an error if it didn't find the value requested.
Using RangeError is nice as it allows code to use array index
inside `nothrow.` But again, can we really review code and say
this will be the case? We'd have to enforce all access to
associative arrays to be done using `in` and checked for null.
Then what use is the  syntax?
Is it recoverable? I would say yes. We aren't actually trying to
access memory outside the application ownership, we haven't put
the system state into a critical situation (out of memory). And a
higher portion of the code could easily decide to take a
different path due to the failure of its call.
"if exceptions are thrown for errors instead, the programmer has
to deliberately add code if he wishes to ignore the error."
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