Hi > So what I noticed that "A Gentle Introduction to Haskell" mentioned > that wild-cards are useful in constructors. For example: > > head (x:_) = x > > So, does that offer any performance benefits over: > > head (x:xs) = x
No. They are exactly the same. _ simply means "a new unique name". > Or is it primarily to indicate to the coder that xs is useless? Yes > I get > the impression it has a very similar meaning to the irrefutable > pattern in regards to not evaluating it when the function is called. > Or am I way off? Way off :-) Nothing to do with irrefutable patterns, or demand of evaluation, its got two uses: 1) Indicate to the reader that this argument is never used 2) Save you coming up with a name for the argument Thanks Neil _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
