On Thu, Jan 15, 2009 at 12:38 PM, Duncan Coutts <duncan.coutts@worc.ox.ac.uk
wrote:
On Thu, 2009-01-15 at 19:46 +0000, Andrew Coppin wrote:
PS. As a small aside... Is the Monoid class actually used *anywhere* in all of Haskell?
Yes.
They're used quite a lot in Cabal. Package databases are monoids. Configuration files are monoids. Command line flags and sets of command line flags are monoids. Package build information is a monoid.
It is also used in the Foldable class which is a nice interface for traversing/visiting structures. Binary serialisation is also a monoid.
The Writer Monad requires that you give it a Monoid for it to do its work properly.
Duncan
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