Tony Morris

Yes they do, since the denotational semantics of IO is "whatever." This is a valid criticism of IO. But IO is as referential transparent as [], Maybe, ((->) t), etc.. If the focus were shifted to the correct properties of IO, we could all work toward something better imo.

Can you elaborate? When I i.e. readFile in haskell, it is IO right? How is that referential transparent? I cannot replace the call with its value the next time, since the file might not exist

I do not know the *> operator?! I presume, that in the second example, readFile is only executed once, whereas in the first example, it is executed twice. The file could change in between no?

Hehe I would love to attend, once I find the possibility. I would like to understand this... is it because it is not executed until you use whatever is inside the IO context?