Use of special characters in function names

Question

In Ruby, a standard convention is to use a question mark at the end of a method name to indicate the method returns a boolean result:

[].empty?   #=> true

Another standard convention is to end a method name with an exclamation point if the method is destructive (that is, it modifies the original data):

mylist.sort! # sort mylist in-place

Recently I have seen these same conventions used in Scheme. Which makes me wonder, what other languages use/support this convention? Are there any other special characters that are commonly used for naming by these or other languages?

Answer 1

If you count Javascript as a language, many frameworks seem to make use of the '$' character to mean "Selector"; For example, one might use $("id-of-some-item") in Prototype.js or $("#id-of-some-item") in jQuery to select a tag that was written <div id="id-of-some-item">. The use of these selection functions is actually quite complicated and powerful (if you're interested, check out their supporting documentation at prototypejs.org and jquery.com), but they boil down to doing something I consider semantically similar to what you've indicated.

Again, this is assuming you count Javascript as a language.

Answer 2

Prepending "@" to a method name (or any identifier) in C# allows you to name that method with a normally-reserved keyword.

void null() {}
// Invalid token 'null' in class, struct, or interface member declaration

void @null()
// compiles

Don't do this; it's mainly for machine-generated code, like datasets. MSDN page on the topic.

Answer 3

I'm not a big fan of special characters in function names, but then I'll also beat to death, with a stick of wet celery to tease out the pain, anyone I find putting spaces into file names :-)

The ? variant can just as easily be done with something like isEmpty() and the ! variant with sortInPlace().

English is a very adaptive language, even without the punctuation.

In either case, my languages of choice (C and Java) use punctuation for all sorts of other things. Having them in identifiers as well would make the lexical analysis a nightmare.