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

wren ng thornton writes:

On 12/28/11 10:23 AM, Jon Fairbairn wrote:

...

Thiago Negri writes:

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Lazy evaluation is one implementation of non-strict semantics, where the arguments are evaluated only when they are needed.

I would say this:

* non-strict semantics require that no argument is evaluated unless needed.

I'm not sure that's quite right.

I’m sure it’s not right (as was pointed out a while ago). I was in too much of a hurry to get to the next bit, namely giving a description of the difference between non-strict and lazy. Perhaps what I should have said to be almost as succinct but this time accurate is “non-strict semantics requires that the evaluation strategy terminate if there is any evaluation strategy that terminates”? -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk