29 May
2007
29 May
'07
11 a.m.
On Sun, 27 May 2007, Andrew Coppin wrote:
such that a Reader is created with an initial list, and the read function fetches 1 element out of that list. That is, the expression "x <- read" will take the head element of the list and put it into x, keeping the tail to be read later.
(Oh yeah - and apparently that clashes with Prelude.read. Oh well!)
I can't figure out how to implement this... The closest I managed was to make a Reader object also contain a function that tells (>>=) what to do to the Reader object you're binding against... But that seems to be horribly buggy.
Confusingly MonadReader and MonadWriter in the Monad Template Library are not quite counterparts. Reader does not consume its input, Writer does not overwrite its output.