Function type naming conventions

[Dan Smith]

On Jan 4, 2013, at 3:46 PM, Dan Smith <daniel.smith at oracle.com> wrote:

> On Jan 3, 2013, at 2:07 PM, Dan Smith <daniel.smith at oracle.com> wrote:
> 
>>> I'm sure I'll never remember whether IntFunction is int -> int, T -> int, or int -> T, so it'll trip me up a little each time I read it.
>> 
>> Stephen Colebourne makes a similar comment in the comments list.  His suggestion is to use a different base name for functions that return primitives -- we already have "Predicate" and "Block"; now we just need "IntThingy" and "DoubleThingy".  Stephen suggests "CalcInt", which I don't love, but maybe there's a word out there that nicely conveys the concept much like "Predicate"?
> 
> I did a little Googling: "predicate" is a.k.a. "boolean-valued function".  "Real-valued function" and "integer-valued function" are also fairly widely-used terms.  But I didn't come across any more concise terms for those...

I've been kicking around an idea in my head for the last few days and haven't rejected it as horrible yet:

"integer-valued function" (and "foo-valued function," generally) is the appropriate, widely-understood term for functions that output integers [1][2][3][4].  So let's just say that, slightly abbreviated:

IntValFunction<T> // T -> int

The meaning should be unambiguous.  That leaves "integer function" (and "foo function," generally) to refer to functions that input integers.  Again, that general form is widely-understood terminology [5][6].

IntFunction<T> // int -> T

The weak point is that both terms are abused in some contexts (such as [2], I think) to refer to int->int.  But since we've got "integer operator" in the mix as well, I think it's fairly straightforward to disambiguate.

—Dan

[1] http://www.proofwiki.org/wiki/Definition:Integer-Valued_Function
[2] http://alexandria.tue.nl/repository/freearticles/597509.pdf
[3] http://en.wikipedia.org/wiki/Real-valued_function
[4] http://en.wikipedia.org/wiki/Boolean-valued_function
[5] http://php.net/manual/en/ref.strings.php
[6] http://docs.racket-lang.org/reference/pairs.html#3.9.7