How to make long parameter lists readable?

Question

I've developed a natural aversion to long parameter lists in functions. While this is to some extent a good thing, sometimes long parameter lists are the lesser of two evils compared to code duplication or ridiculously long functions due to "manual inlining". What's a good way to at least make some of these monstrosities human-readable? For example:

SomeClass[string] someFunction(SomeClass!(TemplateParam) foo, 
    string[][string] someAA, uint[] dataToProcess, SomeEnumType flag) {
    // Do stuff.
}

This doesn't score high on the readability scale, but four parameters is pretty reasonable in a lot of cases.

Answer 1

For this kind of situation, I tend to format it like this:

SomeClass[string] someFunction(
    SomeClass!(TemplateParam) foo, 
    string[][string] someAA,
    uint[] dataToProcess,
    SomeEnumType flag
)
{
    // Do stuff.
}

Answer 2

• for the sake of readability - put each argument on new line
• for the sake of usability and better API desgin - group related arguments into new classes, thus shortening the number of arguments.