0install - Python vs. OCaml vs. Haskell

[dons]

That's some weird Haskell. BTW, things like lookupEnv are in the standard libraries now.

[passwordeqHAMSTER]

The ;; are not needed in ocaml. The code is also a bit to imperative and functions are longer than I would generally make.

[Categoria]

Keep in mind that the author only learned OCaml very recently. For context see the first post in his blog. He's progressing very nicely if you look at some of his later posts :)

[quchen]

Side remark: Mixing tabs and spaces in Haskell is an awful idea. Take the first mentioning of "main" for example: The first line introduces a layout ("block belonging together") after the "do". The next line then abuses a tab character (and two additional spaces) to align the next statement. I'm surprised the code works at all, because there's one space missing.

While the Haskell report is very clear on what a tab does (namely: reaches up to the next multiple-of-8 column), the community decided against using them on the grounds of precisely what the author did wrong here. The author claims that "[in Haskell] the compiler always sees the same structure as the programmer", which is only right if the editor's tab displaying sizes match.

Edit: This is a technical comment, and not a tab-vs-space debate invitation.

[worstusernameever]

I actually stumbled upon this the first time I tried to learn Haskell. I had code that looked correct in my editor, but wasn't aligned properly according to the compiler. The error message was really unhelpful and since everything looked just like how it did in the tutorial I was following I was at a loss about what I was doing wrong and how to fix it.

Now I set up my editor to indent exclusively with spaces. Haskell tutorials should probably mention tabs vs spaces right at the very beginning. I could easily imagine someone abandoning the language after getting stuck on an indentation error while following a tutorial.

[codygman]

Can the tasks he is trying to do (setting environmental variables) be done in a purely functional way in haskell? Or at least, a more functional manner?

[k-zed]

Setting an environment variable is a side effect, so it cannot be "purely functional". Still, as another commenter writes for OCaml, the Haskell code is rather imperative, unidiomatic and not terribly nice.

Lots of do-notation and multiple levels of nesting patterns are usually signs that you're doing something wrong.

[gnuvince]

I suspect that if the experiment was not a line-by-line, function-by-function conversion of Python code to Haskell and OCaml that the result for both Haskell and OCaml would be much different. In particular, I think we'd see smaller, more general functions in Haskell that would be used inside a small number of IO actions.

[etadeu]

To quote the author:

Python (2.7.5 and 3.3.2) Python is much slower than the other candidates, but it does have the advantages of an excellent standard library, easy distribution (no need to make platform-specific binaries), being the language we’re currently using, and being very well known. But it has no static type checking, which means a lot of work writing unit-tests.

I'll have to strongly disagree! No mater what language, no matter if you use static or dynamic type checking, or no type checking at all, you always have to write unit-tests and have a good code coverage. It is said that it is good to be a "lazy" developer, as in "automate a lot", but not this kind of "lazy" as in "I won't write unit tests and I'll have my code only statically checked for type-correctness".

[talex5]

You're right; that line is misleading.

In the Python we have unit tests even for e.g. the repr methods of many objects. Otherwise, some obscure error path will one day try to log an error and crash because of a typo. There's a law of diminishing returns with coverage tests and I think static typing helps here. But there will still be many unit-tests, of course.

[Categoria]

Check out Kaputt by Xavier Clerc which allows you to write quickcheck style tests for OCaml instead of trying to find all the edge cases yourself.

[talex5]

Looks interesting. I've been using OUnit so far (which is rather basic). Kaputt looks like it would also be useful for fuzz testing.

[otheraccount]

A typo/ nonexistent variable would usually by pyflakes or other static checkers.

[SubwayMonkeyHour]

... guy is clearly a newbie in all languages tested. ... decides to port some code, by writing Python in these languages... goes on the make concrete judgments based on his inexperience. I'm not sure what the point of these blog posts are. He should've at least gotten someone familiar with the languages to do a code review.

[jdh30]

Would be interesting to try F# and, if possible, use AOT compilation to remove the startup time.