Re: [stack] What does "concatenative" actually mean?

William Tanksley scripsit:

> The truly pure functional languages, like Haskell, have a mathematical
> model for state-changing effects, like objects and I/O. The problem is
> that purely functional languages don't express what order their
> operations will occur in; they just tell the computer what operations to
> do, and let the compiler figure out the best order. So Haskell provides
> a mathematical construct called a "monad". Monads can mathematically
> only be evaluated in order, so the compiler receives enough information
> to know what order to execute your code in.

You don't really need monads: they are just a convenience, because
it would be painful to thread state through every function in
your program just in case a callee wants to use some of it; see
http://lambda-the-ultimate.org/node/1155#comment-12726 for details.
In Joy, the equivalent of the I/O monad is the simple fact that "read"
has a stack shape of F -> F O, preserving the F object on the stack.

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