PAUL IS BOTHERED

2010-05-09

You can talk all you want about ‘practicality,’ but one way in which I see functional languages will ALWAYS beat imperative is the built-in love of lists. I simply can’t express my distaste for always writing:

    import java.util.Collection;
    import java.util.Iterator;
    
    // crap elided
    
    Iterator<String> iterator = myCollection.iterator();
    
    while (iterator.hasNext()) {
        doSomethingWithString(iterator.next());
    }

over, say:

    (map do-something-with-string my-collection)

But Paul! says you, Java gives you static typing! The Scheme example above doesn’t, so it can get away with that kind of dynamic-language brevity! Well, so does Haskell:

    map doSomethingWithString myCollection

and SML:

map(doSomethingWithString)(myCollection)

For fun, lets just see it in a smattering of other languages I’ve used. Ruby:

    my_collection.each { |x| do_something_with_string x }

Erlang:

    lists:foreach(fun do_something_with_string/1, MyCollection),

Common Lisp:

    (mapcar #'do-something-with-string my-collection)

Naturally, this isn’t even the whole picture. The example assumes you’re iterating for side effects; if you needed the list with its elements transformed, that would be another 5-7 lines of Java. And the list can only exist because it was constructed to begin with, which if you did it in another class, requires 3-6 more import declarations there.

I know its trendy to hate on Java, and I’ve mentioned before that PL hating like this is unproductive. Still, we use and work with variable-sized lists all the time, and what functional designers figured out (long, long ago) is that it’s quite nice to have them built-in.

Bleh, sorry. Android programming is fun, despite the Java.

I did say “imperative” above, not just Java. Kind of a misnomer, as CL and Ruby, above, provide one-line map and are arguably imperative. In that case, I let my biases shine through and used “imperative” interchangeably with “luddite.” But let’s never forget our buddy C++:

    #include <list>
    using namespace std;
    
    list<string>::iterator iter;
    
    for (iter = my_collection->begin(); iter != my_collection->end(); ++iter) {
        do_something_with_string(*iter);
    }

PUKE

More Paul

less lame!

PAUL IS BOTHERED