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Comment by PeterisP | Hacker News Reader

Be able to clearly reason about the space complexity of code.

Even quite short parts of code can have an unexpected (at least unexpected to me) explosions of thunks, and it's quite difficult (at least to me) to find out where/how strictness markers should be added so that the code wouldn't generate the totally unneeded gigabytes of temporary data that I see in the memory profiler.

It's quite easy to reason about the correctness and results of Haskell code execution, but it's hard to reason how exactly that code will be executed in ways that have an extreme effect on performance - not tenfold, but e.g. exponential relative to dataset size.

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Another worthy topic of debate that is completely unrelated to my question. Types and laziness are independent -- at least to the degree needed to provide an answer to my question.

> Types and laziness are independent

I think they are directly linked. If I have to worry about arbitrary types, my code can never be robust for the environment it runs in without raising some generic exception. This is the lazy approach. In a dynamic language, everything can be boxes to a static list of flexible types and is by default, meaning my code is succinct. This doesn't address the question (which is a strawman), but is the heart of the debate about static vs dynamic typing. Getting things done faster (with some guarantees) vs many guarantees (but not all) at a slower rate of progress (because you have to essentially duplicate code at a higher level, that the dynamic interpreter is already doing).

I can't actually understand anything you've said. You are using this definition of lazy, right? https://en.wikipedia.org/wiki/Lazy_evaluation

That's not true. When the language is lazy, you can't give a different type to one expression that's lazy and one expression that's strict. You can write hacks into the language that tell the compiler to evaluate certain expressions strictly, but you can't capture this in the type system when the language is lazy by default. On the other hand, this is perfectly possible in a strict language.

Firstly, that falls under my "at least to the degree needed to provide an answer to my question" rider. Secondly, no you can't type the values but you can type the consumers of the values, i.e. the functions: http://h2.jaguarpaw.co.uk/posts/strictness-in-types/

Ah, didn't realize the original question was limited to comments on dynamic typing. Regardless, that's a clever article, and an interesting tradeoff.

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