From f06f075517e35a64781a9ec6b773a5aba0b8e36d Mon Sep 17 00:00:00 2001
From: Phil Budne <phil@ultimate.com>
Date: Wed, 2 Mar 2016 15:40:52 -0500
Subject: [PATCH] fix subtraction with relative values
 (relative-relative)=absolute!

---
 tools/as7 | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/as7 b/tools/as7
index 333c340..41b0c09 100755
--- a/tools/as7
+++ b/tools/as7
@@ -465,15 +465,29 @@ sub parse_expression {
 
 	if ($op eq '+') {
 	    $word += $syllable;
+	    $flags |= $sylflags;
 	}
 	elsif ($op eq '-') {
 	    $word -= $syllable;
+	    if ($flags & $RELATIVE) {
+		# relative-relative => absolute!
+		if ($sylflags & $RELATIVE) {
+		    $flags &= ~$RELATIVE;
+		}
+		# else: relative-abs => relative (no change)
+	    }
+	    else {		# word is absolute
+		if ($sylflags & $RELATIVE) {
+		    err('A', 'absolute value minus relative??');
+		}
+		# else: absolute-absolute => absolute (no change)
+	    }
 	}
 	else {
 	    $word |= $syllable;
+	    $flags |= $sylflags;
 	}
 	$word &= 0777777;
-	$flags |= $sylflags;
 	printf("\tsyllable: %#o word: %#o\n", $syllable, $word) if ($debug);
     }
 }