On 29-Jan-09, at 1:44 AM, Alex Ryu wrote:
Hello I would like to do something similar to the following within my C program:
char* condition = "(2 < 4) & (3 > 7"); int boole; ... boole = evaluate(condition);
where evaluate is a scheme function already written and compiled by gsc. Most of the documentation I have seen relates more to the reversed situation - calling C functions from scheme. I have taken a look at the client example program in the tests directory, but it is not clear to me exactly how the string is treated by scheme - ie, in what form it is going to be, if that makes any sense. Obviously I would prefer it as a list of some sort, but I don't know if that's possible. I am using Linux and gcc 4, if that makes a difference. Thanks for your time Alex
The example code in tests/client.c and tests/server.scm is very close to what you want. One difference is that you want the function to return a boolean. The other difference is that in your example you are using an infix expression. Is this really what you want? The code in tests/server.scm uses Scheme's normal prefix syntax. If you really want infix then you could change the eval-string function in tests/server.scm to be
(c-define (evaluate str) (char-string) bool "evaluate" "extern" (catch-all-errors (lambda () (eval (read-from-string (string-append "\" str ";"))))))
This will use Gambit's SIX parser (Scheme infix syntax extension).
This is untested code.
Marc