Yet Another Monad Tutorial (part 7: state monads)

[mvanier]

In this article we'll look at a very interesting class of monads: state monads.

Comments

Excellent Series on Monads.

[anonymous]

Your articles on Haskell are the most understandable (and well-written) I have read.

I have the book "Real World Haskell", but am learning far more from you just by concentrating on your articles on Monads.

Thank you, and please keep blogging.

Re: Excellent Series on Monads.

[mvanier]

Thanks for the compliment! I'm glad you're getting something out of the tutorials. I plan to start up again in the new year, so stay tuned.

typo: return type of runState

[ext_697914]

Hi Mike,

Under the section where runState, evalState and execState functions are shown, there is a typo in "runState returns the final (state, value) tuple". It returns the final (value, state) tuple.

Anyway, thank you for writing this series of tutorials! I've read up to this one and it's probably the clearest tutorials on monads I've read. I think the first tutorial in this series is a classic, especially the way you explain what a monad is.

Re: typo: return type of runState

[mvanier]

Thanks for the bug report! I've fixed it. And thanks for the comments -- tell your friends :-)

[grkuntzmd]

I started teaching myself Haskell several months ago and have read both "Learn You a Haskell" and "Real-World Haskell", as well as several online tutorials, particularly on monads. I understood monads on an academic level, but could not "internalize" them. That is, until I read your tutorial series, especially the segment on the state monad. Yours is the clearest explanation of this difficult subject that I have seen to date.

Perhaps your might consider collecting your series into a single document and either self-publishing a booklet on Amazon, or at least producing a PDF for people to download. I know that I would add it to my reference library and refer others to read it.

Thanks for explaining this complex subject very clearly.

-Ralph

[mvanier]

Ralph,

Thanks very much for your kind words! I'll consider publishing this at some point, but I still have stuff to add e.g. on monad transformers.

Mike