Initial file

examples/ffi/sub-bignums.h

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+#include "cyclone/types.h"
+
+// Some custom function to speed-up code
+mp_int sub_big_nums(void *data, mp_int bnx, mp_int bny) {
+    alloc_bignum(data, bn);
+    BIGNUM_CALL(mp_sub(&bnx, &bny, &bignum_value(bn)));
+
+    return bignum_value(bn);
+}

examples/ffi/sub-bignums.scm

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+;; A basic example of subtracting 2 bignums using the FFI.
+;;
+;; This example is notable because we need to pass the
+;; current thread's data object to C so that we can pass
+;; it along to functions in the Cyclone runtime.
+;;
+(import (scheme base) (scheme write) (cyclone foreign) (srfi 18))
+(include-c-header "sub-bignums.h")
+
+(c-define sub-big-nums bignum "sub_big_nums" opaque bignum bignum)
+
+(write
+  (sub-big-nums 
+     (current-thread-data)
+     999999999999999999999999
+     222222222222222222222222
+     ))