Comments on: The barbarism of the for loop

By: Keith Elder

Keith Elder — Thu, 17 Jan 2008 21:24:42 +0000

I don’t think it is premature optimization if I know that I am dealing with a zero indexed array of data. The fastest way to process through that data is a for loop. Now with that said that doesn’t mean I will use a for loop I may use a foreach because it is more convenient for me and I honestly could at that moment care less about speed.

I write mainly in C# so I don’t have a “map” function. My point is it is still useful and to say it just shouldn’t ever be considered or used because you have to think more to use it doesn’t equate to throwing it out of the tool bag all together.

-Keith

By: Adam Keys

Adam Keys — Thu, 17 Jan 2008 17:54:58 +0000

Keith, my feeling is that if you’re using a for loop just to speed up your code, you’re engaging in premature optimization. For loops often lead to fence post errors. Plus, its just more to think about.

Something like foreach at least gets you away from fence post errors. Using higher-order iterators like map further reduce the amount of code you need to write in all sorts of common cases.

By: Keith Elder

Keith Elder — Mon, 14 Jan 2008 19:06:11 +0000

Hi, found your blog through OBJO on Twitter. He and I met at Codemash this past week.

For loops have their place in the programming paradigm. I have done a lot of benchmarks in languages over the years and when you need to loop through something the for loop is still faster than a while or a foreach or whatever other shortcut syntax you boil it down to.

Just because it isn’t pretty doesn’t mean it shouldn’t still be used.

By: Adam Keys

Adam Keys — Mon, 14 Jan 2008 18:51:28 +0000

I’m also adding those who do insane graphics programming (3D stuff, etc.) Basically, if you are anyone’s inner loop, then you are a beautiful flower who can use whatever ugly constructs you need in order to squeeze out cycles.

Everyone else still using a for loop is on notice.

By: Adam Keys

Adam Keys — Mon, 14 Jan 2008 18:02:44 +0000

The jury is still out for me on list comprehensions. That said, there is something distinctly cool about doing Pythagorean triplets in Erlang with them:


pyth(N) ->
    [ {A,B,C} ||
        A <- lists:seq(1,N),
        B <- lists:seq(1,N),
        C <- lists:seq(1,N),
        A+B+C =< N,
        A*A+B*B == C*C 
    ].

By: Phil

Phil — Mon, 14 Jan 2008 17:51:01 +0000

One of these days someone is going to have to explain how list comprehensions are more than just a workaround for Python’s extremely lame lambda support. How is that more expressive/powerful than map?

By: Kevin smith

Kevin smith — Tue, 08 Jan 2008 15:18:45 +0000

There’s also pure map:

do_something(Data) ->
F = fun(Item) -> io:format(“~p~n”, [Item]) end,
lists:map(F, Data).

And filter:

do_something(Data) ->
F = fun(Item) -> Item < 5 end,
lists:filter(F, Data).

fold, foldr, and flatmap are also useful.