On Feb 10, 2008 1:42 PM, Sebastian Sylvan <[EMAIL PROTECTED]> wrote: > > > On Feb 10, 2008 1:34 PM, Michael Feathers <[EMAIL PROTECTED]> > wrote: > > > On a lark, I loaded this into Hugs this morning, and it didn't complain: > > > > > > data Thing = Thing (Integer -> Integer) > > > > > > > > But, I've never seen that sort of construct in an example. Do people > > ever embed functions in ADTs? > > > Yes, this is quite common. Here's a quick example (untested): > > data MyMap key value = M (key -> Maybe value) > > lookup (M m) key = m key > insert (M m) key value = M (\key' -> if key' == key then Just value else m > key') > > This is a naive data structure for storing a map as a function from the > key to the value. Not very efficient, perhaps, but you use similar concepts > in more useful scenarios (e.g. the State monad). >
Perhaps I should add an empty MyMap too: empty = M (\_-> Nothing ) -- Sebastian Sylvan +44(0)7857-300802 UIN: 44640862
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