Casting between native types

jank has two primary means of casting between native types.

1. cpp/cast
2. cpp/unsafe-cast

They both have the same syntax, but they perform different actions.

cpp/cast

This is the most common style of cast which you’ll see in jank. It closely maps to C++ static_cast, but it has additional functionality to support jank’s trait conversions. This will allow you to cast to/from jank runtime object and supported native C++ values.

(fn [o]
  (let [f #cpp 3.14
        ; Normal static_cast support.
        i (cpp/cast cpp/int f)
        ; Explicit trait conversion, since `o` is a jank object.
        oi (cpp/cast cpp/int o)])

cpp/unsafe-cast

When cpp/cast is not enough, jank supports a more cutting cast which is the equivalent of C-style casting in C++. This is a combination of static_cast, reinterpret_cast, and const_cast. For example, if you need to cast between unrelated pointer types, cpp/cast will not work, but cpp/unsafe-cast will. However, note that cpp/unsafe-cast does not support trait conversions. It is solely dedicated to native type construction and reinterpretation.

(let [s #cpp "meow"
      us (cpp/cast (cpp/type "unsigned char*") s)])