On Monday, 8 April 2019 at 11:58:49 UTC, Ron Tarrant wrote:
And while I'm asking, does an underscore have special meaning when used either at the beginning or end of a variable name?
In D, @ is used as Adam has explained as a prefix indicating attributes (either user-defined ones or, confusingly enough, some of the standard ones).
The only other example of language using @, in an almost but not quite completely different way, is C#. It's also a prefix that allows you to define names that would collide with reserved words, for example string @class = "menu"; Of course you should never do this unless you absolutely need for interop.
Underscore prefixes are used in some languages by pure user convention mainly for private members (fields), to avoid name clashing. For example in D you could have a public property length and a private member _length.
Python takes this a step further. Since it supports classes but no public/private visibility at all, users and IDEs have convened to use (one or two) underscore prefixes to signal members that aren't meant to be accessed publicly from outside the class, even if there's nothing stopping you (besides auto code completion not showing them).
For C and C++ the convention (recognized by the standards) is different: names prefixed by any number of underscores are all reserved; basically because the global namespace is so badly polluted already. In this case I've seen some other annoying conventions, for example private member variables being prefixed with m_
