#Type to learn 4 hack how to#
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First, the typechecker is designed for instant feedback, even when working in very large codebases. These downsides aren’t present in Hack, for two reasons.

#Type to learn 4 hack code#

You also have to write out types everywhere, making your code more verbose and harder to change. Before you can run your program, you have to wait for it to compile, and depending on the language and the size of the program, that can take a long time.

In the classic debate, the disadvantage that supposedly accompanies these features is a drag on development speed. Static analysis capability makes refactoring easier, as it can ensure that there are no breakages at module boundaries. Because it doesn’t need to run the program, it catches problems earlier in development, which saves development time. The typechecker is able to look for mistakes without running the program, so it can catch problems even with codepaths that aren’t run during testing. The argument in favor of Hack typechecking sounds similar to the argument often used in favor of statically typed languages.

#Type to learn 4 hack how to#

In this chapter, we’ll see why you should use the typechecker, how to use it, and how to write type annotations for it. Hack retains the flexible, rapid-development character of PHP, a dynamically typed language, while adding a layer of robust, sophisticated typechecking. The philosophy of Hack rejects this as a false dichotomy. It’s often presented as a choice between the robustness of static typing and the flexibility of dynamic typing. The choice between statically typed languages and dynamically typed languages is endlessly debated among programmers.

To enhance the typechecker’s ability to do this, Hack allows programmers to explicitly annotate the types of some values in their programs: function parameters, function return types, and properties. It analyzes Hack programs statically (i.e., without running them) and checks for many different kinds of errors, which prevents bugs at an early stage of development and makes code easier to read and understand. The typechecker is the flagship feature of Hack.