On Thursday, 21 January 2016 at 23:05:51 UTC, Dibyendu Majumdar
wrote:
I am puzzled as to why there is @nogc on the one hand and
simply nothrow on the other? Why are some attributes prefixed
with '@' while others aren't?
Regards
Short answer: It's for historical reasons; it would not be done
this way today, but cannot be changed without breaking valid code
already in the wild.
Longer answer: The ones prefixed with @ are not keywords. This is
good, because it means that they are not reserved, and may be
used as identifiers as well.
This will compile fine:
void nogc(int nogc) @nogc nothrow {
}
This won't, though:
void nothrow(int nothrow) @nogc nothrow {
}
When the process of designing D began, people didn't realize just
how many attributes would end up being added to the language. At
some point, it became clear that it was both undesirable and
unnecessary to forbid all attribute names from being used for
other purposes elsewhere in D's grammar. The solution was to
begin prefixing @ to new attributes.
Adding the @ to the old attributes was discussed as well, but it
didn't seem worth the code breakage.
A revision of D that wasn't constrained by backwards
compatibility would almost certainly either require all
attributes to be prefixed by @, or change the grammar such that
attribute names could be reused as identifier names without
introducing ambiguities.
