Ronald Guida wrote:
Given the question "What is a Monad", I would have to say "A Monad is a device for sequencing side-effects."
There are side-effects and there are side-effects. If the only monad you use is Maybe, the only side-effect you get is a slight warming of the CPU. Dave Menendez pointed to that fine Wadler link earlier. Please read it. To wit, in Section 2: "Explaining Monads" the "essence of an algorithm can become buried under the plumbing required to carry data from its point of creation to its point of use." Monads can help keep the clarity of your code untrammelled by providing implicit plumbing, "side-channels" if you prefer, when data is moved around. In fact if you follow Wadler all the way to his monadic expression evaluator, you see that you could modularize your code in awesomely cool ways. You get to see how the kernel of the expression evaluator could be written for a generic monad and compiled once-and-for-all. Any additional feature (the "variations") is coded by enriching the monad. Monads are powerful devices for modularizing code. Available for free. Only in Haskell (thanks to type classes!). Get them today. "Side-effects" is a piece of linguistic cruft played fast-and-loose by too many people in this game. "Sequencing" suffers the same disease. -- View this message in context: http://www.nabble.com/Explaining-monads-tf4244948.html#a12126170 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.