Hi Heinrich,
Thanks for confirming my concepts. It took me a long time pondering over
what it meant to be purely functional.
Great articles btw (+1).
On 16 March 2015 at 19:41, Heinrich Apfelmus
Karl Voelker wrote:
On Sun, Mar 15, 2015, at 09:17 AM, Simon Kitching wrote:
And AIUI the Haskell compiler/runtime can postpone evaluation of any function (laziness), or reorder function calls whever it thinks this good.
It's not that it "can" but that it must. Haskell's evaluation strategy is a part of the language specification.
Consider this expression:
let f = 1 : f in take 5 f
You can paste this into ghci and feel confident that it's going to terminate. You're not at the whim of the runtime.
I think you may find these articles interesting:
https://wiki.haskell.org/Lazy_evaluation https://wiki.haskell.org/Non-strict_semantics
Strictly speaking, the Haskell language standard only specifies that Haskell has non-strict semantics, not that it needs to be evaluated using lazy evaluation.
Of course, the two are related. I have tried to expand on the details here:
https://hackhands.com/non-strict-semantics-haskell
Best regards, Heinrich Apfelmus
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