[the_af]

This is interesting, because the well-known paper "Why functional programming matters" identifies two key aspects of FP: higher-order functions and lazy evaluation. I wonder if John Hughes has reviewed his opinion on this, or if the FP community thinks the paper is no longer an accurate insight into FP...

In particular, I'm thinking of the last paragraph of Hughes' conclusions:

"It is also relevant to the present controversy over lazy evaluation. Some believe that functional languages should be lazy, others believe they should not. Some compromise and provide only lazy lists, with a special syntax for constructing them (as, for example, in SCHEME [AS86]). This paper provides further evidence that lazy evaluation is too important to be relegated to second-class citizenship. It is perhaps the most powerful glue functional programmers possess. One should not obstruct access to such a vital tool."

Maybe it turned out that practical evidence has shown that lazy evaluation wasn't as important for modularity as Hughes thought, or at least that its drawbacks have been found unacceptable in practice?

[tel]

I think that there is no cut and dried answer. Laziness appears to dramatically improve modularity, but it's unclear whether all of the tradeoffs are worth it. It's difficult to analyze the downsides still since (a) more research is needed and (b) a lot of it can be shrugged off as "weirdness", but it's clear that there are reasons to prefer strictness as well as to prefer laziness.

I've grown to be of the opinion that neither is best and that languages ought to be developed which allow free and clear choice between evaluation strategies throughout. Lazy defaults at the right times and clear strictness types might be a way forward, but it's hardly anything I have expertise in.