This is a spinoff of Issue 5140 , see there for more info and discussions. Inside a function __function (or __func) is the alias to the function itself. It allows code like this, this recursive code will keep working even if "fact" gets renamed, it's more DRY (http://en.wikipedia.org/wiki/Don%27t_Repeat_Yourself ): long fact(long n) { if (n <= 1) return 1; else return n * __function(n - 1); } void main() { assert(fact(20) == 2_432_902_008_176_640_000); } See a better explanations and some examples of __function: http://rosettacode.org/wiki/Anonymous_recursion It's like the difference between D OOP and Java, this is Java-like code: class Foo { Foo(int x) {...} void bar(Foo f) { Foo g = new Foo(5); ... } } This is one possible equivalent D code, it contains the name Foo only once: class Foo { this(int x) {...} void bar(typeof(this) f) { auto g = new typeof(this)(5); ... } } Another use case for __function: http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.learn&article_id=26404
It's easy to do at the library level: auto recursion(string Fun = __FUNCTION__ , A...)(auto ref A a) { import std.typecons: tuple; mixin("return " ~ Fun ~ "(" ~ a.stringof ~ "[0..$]);"); } used like this: long factorial(long a) { if (a <= 1) return a; else return a * recursion (a-1); } void main() { auto a = factorial(20); } So maybe this one could be closed as WONTFIX ?
@NilsLankila updated dlang/dmd pull request #11538 "add `__traits(getCurrentFunction)`" fixing this issue: - fix issue 8109, 9306, add `__traits(getCurrentFunction)` This new traits is a shortcut allowing to call the function we are in without using `mixin` and `__FUNCTION__` tricks. https://github.com/dlang/dmd/pull/11538