From 9e727697d372fce0803bfd5b5d9ef6ca774ac536 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Tue, 9 Mar 2021 00:24:26 -0600
Subject: [PATCH] Add a helper function to get the sign bit.

---
 math2.asm | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/math2.asm b/math2.asm
index 9c9cdc6..3f353b3 100644
--- a/math2.asm
+++ b/math2.asm
@@ -128,3 +128,28 @@ lb1      sta   val
          
          creturn 2:val
          end
+
+****************************************************************
+*
+*  int __signbit(long double x);
+*
+*  Get the sign bit of a floating-point value
+*
+*  Inputs:
+*        val - the number 
+*
+*  Outputs:
+*        0 if positive, non-zero if negative
+*
+****************************************************************
+*
+__signbit start
+
+         csubroutine (10:val),0
+         
+         lda   val+8
+         and   #$8000
+         sta   val
+         
+         creturn 2:val
+         end