Haskell has genuine mutable memory, through State and IO.
But even without it, you can emulate mutation in a pure language by threading a "heap" parameter through everything.
There's only at most a log factor of extra space and time required in most computing models to "update" a persistent map (though I'm not sure the best way to encode persistent maps directly in Turing machine tapes, which is the model this result is specifically about)
But even without it, you can emulate mutation in a pure language by threading a "heap" parameter through everything.
There's only at most a log factor of extra space and time required in most computing models to "update" a persistent map (though I'm not sure the best way to encode persistent maps directly in Turing machine tapes, which is the model this result is specifically about)