FFI

C++11 target foreign exports

• Foreign values are resolved dynamically/lazily (and "cached" thereafter), so you don't need to define all of them right away. If needed and missing during runtime, an exception will be thrown. Using a source-level debugger which supports C++ will reveal the missing implementation easily enough.

• To implement foreign values to be exported:

  1. Create a C++ source file (typically in your_workspace/ffi)
  2. #include purescript.h and any other C/C++ dependencies
  3. Use macros FOREIGN_BEGIN( Module_Name ) and FOREIGN_END to delineate your block of exported values.
     For example:
     

     #include "purescript.h"
     
     // Tested with package v4.0.0
     
     FOREIGN_BEGIN( Data_Semigroup )
     
     exports["concatString"] = [](const boxed& s1) -> boxed {
         return [=](const boxed& s2) -> boxed {
             return unbox<string>(s1) + unbox<string>(s2);
         };
     };
     
     FOREIGN_END

• See the standard library implementations for more examples