[Haskell-cafe] strict, lazy, non-strict, eager

[Yves Parès]

See that's typically the speech that scares people away from Haskell...

-- 
The ⊥ is a lie.

2011/12/24 Albert Y. C. Lai <trebla at vex.net>

> Most individuals of the Haskell community have long been maintaining a
> cognitive dissonance; some cases turn into plain hypocrisy. You might
> excuse it for its ancient and prominent origin: Richard Bird and/or Philip
> Wadler themselves wrote like "it is too lazy", "make it more strict" 13
> years ago and surely more. But perpetuating it is not helping.
>
> I have not written this complaint until now because I have been waiting
> for unmistakable evidence, a smoking gun, a red hand so caught that you
> cannot explain away, for example you cannot explain that "one sentence is
> from one person, the other sentence is from a different person".
>
> So, on IRC in #haskell, from the same person, speaking on the same topic
> in the same context, in the same interval of 3 minutes (the first two
> sentences in the same minute):
>
> 1. a function f is strict if  f ⊥ = ⊥
> 2. ⊥ represents any computation which does not terminate, i.e. an
> exception or an infinite loop
> 3. "strict" describes the denotational semantics
>
> People, could you please make up your mind already? It has been more than
> 13 years.
>
> Denotational semantics:
> A. There are no computational steps. There is no termination, and there is
> no non-termination, since there are no steps to finish, and no steps to
> keep going.
> B. ⊥ represents "no information", not "non-termination". There is no
> "non-termination" to represent.
> C. fix id = ⊥ because ⊥ is the least fixed point of id, not because fix id
> non-terminates. There is nothing to terminate or non-terminate.
> D. You say strict, more strict, less strict; non-strict, more non-strict,
> less non-strict. You don't say eager, and you don't say lazy.
>
> Operational semantics:
> A. There is no ⊥; it does not appear in any sequence of computational
> steps, finitely long or infinitely long.
> B. You say eager, more eager, less eager; lazy, more lazy, less lazy; or
> speculative, more speculative, less speculative; or any other adjectives
> for evaluation strategies. You don't say strict, and you don't say
> non-strict.
>
> "Semantics", "semantically speaking":
> A. Which semantics, which semantically? There are two.
> B. Actually there are more, but apparently two is already enough to cause
> all kinds of incoherent statements. If I draw your attention to algebraic
> semantics, will you start saying "it is too lazy, need to make it more
> idempotent"?
>
>
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