Malcolm wrote:
The Haskell Report's definition of `seq` does _not_ imply an order of evaluation. Rather, it is a strictness annotation.
That is an important point.
Now, in the definition x = x `seq` foo one can also make the argument that, if the value of x (on the lhs of the defn) is demanded, then of course the x on the rhs of the defn is also demanded. There is no need for the `seq` here either. Semantically, the definition is equivalent to x = foo I am arguing that, as a general rule, eliding the `seq` in such a case is an entirely valid and correct transformation.
I think it is possible that both camps are right on this issue, as far as Haskell 98 stands. We can translate the definition of x into: x = fix (\y -> seq y foo) Isn't it the case that, denotationally, _|_ and foo are valid interpretations of the rhs? If we want to choose between them then we need something extra, such as an operational semantics, or a rule saying that we prefer the least solution. Perhaps I am just re-stating what Ian wrote in the beginning :) Cheers, Bernie.