From 9162e3691399a1942259f1c7322469cf285d4cc4 Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Sat, 1 Apr 2017 01:02:41 -0400
Subject: [PATCH] Bignum NOT operation

---
 srfi/60.scm | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/srfi/60.scm b/srfi/60.scm
index fc9d31b1..33533f96 100644
--- a/srfi/60.scm
+++ b/srfi/60.scm
@@ -121,13 +121,21 @@
 (define-c lognot
   "(void* data, int argc, closure _, object k, object x)"
   "Cyc_check_int(data, x);
+   alloc_bignum(data, bn);
    if (Cyc_is_bignum(x) == boolean_t) {
-      // uh oh, libtommath doesn't provide this!
-      Cyc_rt_raise_msg(data, \"bignum negation not supported yet\");
+     mp_copy(&bignum_value(x), &bignum_value(bn));
    } else {
-    int result = ~((int)unbox_number(x));
-    return_closcall1(data, k, obj_int2obj(result));
-   }")
+     Cyc_int2bignum((int)unbox_number(x), &bignum_value(bn));
+   }
+
+   // From https://github.com/libtom/libtommath/issues/30
+   /* A one's complement, aka bitwise NOT, is actually just -a - 1 */
+   //CHECK_ERROR(mp_neg(&op->mp, &out->mp));
+   //CHECK_ERROR(mp_sub_d(&out->mp, 1, &out->mp));
+   mp_neg(&bignum_value(bn), &bignum_value(bn));
+   mp_sub_d(&bignum_value(bn), 1, &bignum_value(bn));
+   return_closcall1(data, k, Cyc_bignum_normalize(data, bn));
+   ")
 
 (define bitwise-not lognot)