Question

I have a piece of code where inside a list monad, a function is applied. Function may potentially have non-exhaustive pattern matching for its arguments. Therefore when the function is applied, I might get "Non-exhaustive pattern matching" error. I would like to turn this error into a monadic fail (in this case, an empty list). In other words I would like to get a similar behavior to what happens when Some Pattern Here <- some value inside a do block fails.

Question: Is there an efficient way to make a function application safe? By efficient I mean something that would be analogous to making the applied function match exhaustively and fail explicitly.

Answer 1

One option would be to use spoon to convert the function from one that throws exceptions into one that returns Maybe a values. Then it should be a simple matter of converting Nothing to [].