What do you think of the Lush C interface?

[Edward C. Jones]

I have just stumbled across a language calles "lush". See
"http://lush.sourceforge.net/". What do you all think about the
internals of this language? About the CLush compiler? And the
relationship between Lush and C? Here is a section of the manual:

     1.13. Calling C functions from Lush

     The ability to freely mix Lisp and C code is one of the most
     interesting features of Lush.

     Let's say you have written a C file called titi.c with the
     following content:

       float sq(float x)
       {
         return x*x;
       }

     You have compiled the file and produced the object file titi.o.
     Calling sq from the Lush interpreter is as simple as the
     following. First, dynamically load the object file into Lush

       ? (mod-load "titi.o")

     then, write a lisp function whose only purpose is to call sq.

       ? (de square (x) ((-float-) x)
             (cpheader "extern float sq(float);")
             (to-float #{ sq( $x ) #} ))

     Here is what the above means: (de square (x) ...) means define a
     new Lisp function called square with a single argument x.
     ((-float-) x) simply declares x as float. (to-float ....) converts
     its argument to float (like a cast in C). The sequence #{ .... #}
     allows to insert C code within Lisp code. Therefore #{ sq( $x ) #}
     simply calls the C function sq and returns the result. Lisp
     variables can be inserted in in-line C code by prepending a Dollar
     sign, thus $x refers to the Lisp float variable x. The cheader
     directive allows one to include a string in the "header" section
     of the C files generated by the Lisp to C compiler. We use it here
     to specify the type of the argument and the return value of sq.

     We can now compile the above function using:

       ? (dhc-make () square)

     Two file C/square.c and C/i686-pc-linux-gnu/square.o will be
     generated with the C source and the object code for square. The
     object code will be automatically loaded into Lush. Now square can
     be called from the Lisp interpreter:

       ? (square 5)
       = 25

     In the above example, the to-float casting function was used to
     tell the compiler what type the returned value has. The following
     "cast" functions are available: to-float, to-int, to-double,
     to-bool, to-gptr. These functions cast their argument to the
     corresponding type.