I'm pretty confident that you could write something that was equivalent to all the useful `pickle` calls. By that I mean you'll need to know which operations you'll want to do on your unpickled object:
readAny :: forall c r. [TypeWithReadAnd c] -> String -> (forall a. c a => a -> r) -> Maybe r
readAny types string handle
I think it's fair to say "hey, pickle doesn't require me to list all my types explicitly", but on the other hand, it's not like pickle can conjure those types out of thin air--it considers only the types that are defined in your program.
Here's an example that uses Read as the serialization format and only deals with Int, Char and String; but hopefully you can imagine that I could replace the use of read with a per-type function that deserializes from a byte string or whatever.
I think that's different. `read` requires you to know what you're deserializing up-front, while `pickle` decodes the type dynamically from the data.
Dynamic languages really can have functions whose behavior cannot be expressed as some sort of type signature.
I'm pretty confident that you could write something that was equivalent to all the useful `pickle` calls. By that I mean you'll need to know which operations you'll want to do on your unpickled object:
I think it's fair to say "hey, pickle doesn't require me to list all my types explicitly", but on the other hand, it's not like pickle can conjure those types out of thin air--it considers only the types that are defined in your program.
Here's an example that uses Read as the serialization format and only deals with Int, Char and String; but hopefully you can imagine that I could replace the use of read with a per-type function that deserializes from a byte string or whatever.
https://repl.it/@mrgriffin/unpickle
IIRC the pickle format can define new classes, but I haven't looked at it in over a decade so I might be misremembering.
1 reply →
read :: String -> Maybe PlainPythonObject
read :: String -> Maybe Json
goes a long way.
But as soon as you're using "Maybe", you're impeding much of a type systems strengths, as the article outlined.
2 replies →