hare

commit 35f7eea5187e3d65408df39ad3bba3fed7f271dd
parent edce6d8480b64c9e158414a769a7785b8b97468a
Author: Byron Torres <b@torresjrjr.com>
Date:   Wed, 20 Apr 2022 11:26:45 +0100

time: fix add()

Signed-off-by: Byron Torres <b@torresjrjr.com>

Diffstat:
M
time/arithm.ha
 | 
17
++++++++++++++---

1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/time/arithm.ha b/time/arithm.ha
@@ -5,9 +5,20 @@
 // Adds a [[duration]] to an [[instant]], returning an instant further in the
 // future (given a positive duration), or further in the past (given a negative
 // duration).
-export fn add(a: instant, d: duration) instant = instant {
-	sec = a.sec + d / SECOND,
-	nsec = a.nsec + d,
+export fn add(a: instant, d: duration) instant = {
+	if (d == 0) {
+		return a;
+	} else if (d > 0) {
+		return instant {
+			sec = a.sec + (a.nsec + d) / SECOND,
+			nsec = (a.nsec + d) % SECOND,
+		};
+	} else {
+		return instant {
+			sec = a.sec + (a.nsec + d - SECOND + NANOSECOND) / SECOND,
+			nsec = (a.nsec + (d % SECOND) + SECOND) % SECOND,
+		};
+	};
 };
 
 // Returns the [[duration]] from [[instant]] "a" to [[instant]] "b".