On 9/4/08, Jake Mcarthur
I'm no master either, but how about these simple examples?
data Stream a = Cons !a (Stream a) data Vector3 a = Vector3 !a !a !a
The compiler will certainly be able to infer the strictness itself in most uses, so obviously the purpose for these annotations is not for optimization, but I still would find these annotations useful. This is much like explicitly giving the type for a function. It guides the reader of the program, and just happens to also assist the compiler a little bit.
But why not write your types like: data Stream a = Cons a <Stream a> data Vector3 a = Vector3 a a a in a hypothetical call-by-value language where the <> annotation denotes a lazily evaluated data structure? Does it matter? If it does, then why? If it doesn't, then what would you conclude about whether a language should encourage laziness or strictness?
If optimization is the only reason to worry about strictness, then default laziness really _is_ treacherous. Luckily this is not the case. Laziness is not useful without strictness, otherwise there would never be any evaluation. Understanding how to apply laziness and strictness in different situations is critical to writing efficient but meaningful code in Haskell.
True, but both laziness and strictness exist in strict languages, as well. What if, as a thought experiment, you tried substituting "laziness" for "strictness" in that paragraph of your essay? Cheers, Tim -- Tim Chevalier * http://cs.pdx.edu/~tjc * Often in error, never in doubt "The Internet wasn't created for mockery, it was created to help researchers at different universities share data sets." -- Homer Simpson