[cffi-devel] Re: CFFI + Slime + std::cout

[Stephen Compall]

The following message is a courtesy copy of an article
that has been posted to comp.lang.lisp as well.

Sohail Somani <sohail at taggedtype.net> writes:
> How can I get Slime to relay the output (through std::cout) of a C++
> function called through CFFI through to the REPL?

This is really a CFFI question, and you may wish to send further
followups to the CFFI list instead.  Create a C++ shared library with a
few elements, then load and initialize it using CFFI:

1. A subclass of std::ostream that holds a void(*)(const char*) as an
   instance variable, forwarding all output received to that function.

2. A function like

   extern "C" void init_mylispcout (void (*writer) (const char*));

   that replaces std::cout with an instance of #1.  I forget whether C++
   allows you to change std::cout.

3. A CFFI callback in Lisp to be passed to #2, that writes the output on
   some Lisp stream.

4. A CFFI defcfun on #2.

-- 
But you know how reluctant paranormal phenomena are to reveal
themselves when skeptics are present. --Robert Sheaffer, SkI 9/2003