The big “HACK” signs reputed to adorn the walls of Facebook offices aren't just a command from His Royal Zuckness: The Social Network also uses a programming language called “Hack” and has just given it to the world.
Facebook describes Hack as “a programming language we developed for HHVM that interoperates seamlessly with PHP” and “... reconciles the fast development cycle of PHP with the discipline provided by static typing, while adding many features commonly found in other modern programming languages.”
The Social Network says it already uses Hack for all sorts of things, and likes it because it reduces the likelihood of simple-to-make errors that slow the development process.
“Traditionally, dynamically typed languages allow for rapid development but sacrifice the ability to catch errors early and introspect code quickly, particularly on larger codebases,” Facebook writes. “Conversely, statically typed languages provide more of a safety net, but often at the cost of quick iteration. We believed there had to be a sweet spot.”
“Thus, Hack was born. We believe that it offers the best of both dynamically typed and statically typed languages, and that it will be valuable to projects of all sizes.”
Hack seems to be a superset of PHP and Facebook says “most PHP files are already valid Hack files.”
Features of the new language said to be especially cunning include:
- Type Annotations allow for PHP code to be explicitly typed on parameters, class member variables and return values;
- Generics allow classes and methods to be parameterized (i.e., a type associated when a class is instantiated or a method is called) in the same vein as statically type languages like C# and Java);
- Nullable Types are supported by Hack through use of the ? operator. This introduces a safer way to deal with nulls and is very useful for primitive types that don’t generally allow null as one of their values, such as bool and int (using ?bool and ?int respectively). The operand be used on any type or class;
- Collections enhance the experience of working with PHP arrays, by providing first class, built-in parameterized types such as Vector (an ordered, index-based list), Map (an ordered dictionary), Set (a list of unique values), and Pair (an index-based collection of exactly two elements);
- Lambdas offer similar functionality to PHP closures, but they capture variables from the enclosing function body implicitly and are less verbose.
Code samples to prove the assertions above can be found at the new hacklang.org site erected to promote it and host the open sourcery needed to get Hacking yourself.
Facebook is also throwing a developed day for would-be Hackers capable of getting themselves to Menlo Park on April 9th. ®