The C++ DSL

jank has a domain specific language (DSL) for acessing arbitrary C++ types and values. This DSL is automatically enabled when the jank compiler is expecting a type, such as the first argument to cpp/new, cpp/unbox, or cpp/cast. The DSL can also be explicitly enabled using the #cpp tag.

DSL overview

The C++ DSL can be used to look up both types and values. The jank compiler will ensure that you use a type when you need a type and a value when you need a value.

• (:* t) adds a pointer
• (:& t) adds an lvalue reference
• (:&& t) adds an rvalue reference
• (:const t) and (:volatile t) add the corresponding C++ qualification
• (:signed t) and (:unsigned t) add the corresponding C++ qualification
• (:long t) and (:short t) add the corresponding C++ qualification
• (:array t s?) turns a type into a sized (or unsized) array
• (:fn ret [a1 a2...]) builds a function type
• (t a1 a2...) builds a template instantiation
• (:member t name) nests into a type
• (:member* t mt) builds a pointer to member type
• (:&member t mt) builds a pointer to member value

Let’s take a look at some examples, comparing the C++ representation and the jank representation.

Type examples

std::map<std::string, int*>

(std.map std.string (:* int))

std::array<char, 64>::value_type

(:member (std.array char 64) value_type)

unsigned char[1024]

(:array (:unsigned char) 1024)

unsigned char(&)[]

(:& (:array (:unsigned char)))

int (*)(std::string const &)

(:* (:fn int [(:& (:const std.string))]))

int (Foo::*)(std::string const &)

(:member* Foo (:fn int [(:& (:const std.string))]))

void (*Foo::*)()

(:member* Foo (:* (:fn void [])))

Value examples

jank will never implicitly analyze the C++ DSL for values, like it does for types. You must always tag your DSL form with #cpp to separate it from normal jank code.

std::basic_string<char>::npos

#cpp (:member (std.basic_string char) npos)

std::numeric_limits<long long>::max()

(#cpp (:member (std.numeric_limits (:long (:long int))) max))

&std::pair<int, bool>::first

#cpp (:&member (std.pair int bool) first)