You might want to look at the 'get', 'set' and 'update' rules that DrIFT
can derive. i made them to addres a lot of the same issues you
mentioned.
I personally think it is a travesty that
data Foo = Foo { a :: Int, b :: Char } | Bar { a :: Int }
let x = Bar { a = 4 }
y = x { b = 'x'}
results in bottom rather than just leaving x unchanged.
well, travesty is too strong. but it bugs the heck out of me.
but yeah, the DrIFT code derives functions that pull out fields but
returns them in a possibly failing monad so you can properly handle a
data type with no appropriate field.
John
--
John Meacham - ⑆repetae.net⑆john⑈
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