UFCS is a key feature of D and enables code reusability and scalability through well-defined encapsulation.
UFCS allows that any call to a free function
fun(a) can be written as member function call a.fun().
If a.fun() is seen by the compiler and the type doesn't
have a member function called fun(), it tries to find a
global functions whose first parameter matches that of a.
This feature is especially useful when chaining complex function calls. Instead of writing
foo(bar(a))
It is possible to write
a.bar().foo()
Moreover in D it is not necessary to use parenthesis for functions without arguments, which means that any function can be used like a property:
import std.uni : toLower;
"D rocks".toLower; // "d rocks"
UFCS is especially important when dealing with ranges where several algorithms can be put together to perform complex operations, still allowing to write clear and manageable code.
import std.algorithm : group;
import std.range : chain, retro, front, retro;
[1, 2].chain([3, 4]).retro; // 4, 3, 2, 1
[1, 1, 2, 2, 2].group.dropOne.front; // tuple(2, 3u)
std.range