newlandsvalley
commented
5 years ago In fixing things I've learnt some frightening things about how bloated the generated code can get when dealing with ADTs which have a large number of simple constructors.
- Generic Ord is the worst culprit - this seems to be capable of generating well over a Megabyte of code. After 100 elements are reached, generic ord induces a IncompleteExhaustivityCheck warning. This was fixed by replacing with an explicit Ord instance with hand-crafted code.
- Generic Eq is also problematic, but less bloated. Again, hand-craft the instance.
- Finally, using the Unicode functions isUpper, isDigit and toLower produce a further 300K or so of bloat.
The generic instances also caused long compile times that seemed to grow exponentially with the number of entries.
This is because we have a very large enumerated type for the (128) MIDI instrument names. The problem comes if we want to automatically generate an Ord instance - the code bloat goes through the roof.
The answer seems to be to write an Ord instance by hand by just comparing the stringified version of the names.