hare

commit bab9aefa2f6682aa4a850cde6f3f465a8cf21ef0
parent c2c41c1d2616baedbc419d53e75dcf29c4dae178
Author: Byron Torres <b@torresjrjr.com>
Date:   Tue, 14 Sep 2021 00:21:17 +0100

time: add time::diff

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

Diffstat:
M
time/arithm.ha
 | 
14
+++++++++++---

1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/time/arithm.ha b/time/arithm.ha
@@ -4,7 +4,15 @@
 // 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, b: duration) instant = instant {
-	sec = a.sec + b / SECOND,
-	nsec = a.nsec + b,
+export fn add(a: instant, d: duration) instant = instant {
+	sec = a.sec + d / SECOND,
+	nsec = a.nsec + d,
+};
+
+// Returns the duration from [[instant]] a to [[instant]] b.
+// If a is earlier than b, the duration is positive.
+// If a is equivilent to b, the duration is zero.
+// If a is later than b, the duration is negative.
+export fn diff(a: instant, b: instant) duration = {
+	return ((b.sec - a.sec) * SECOND) + (b.nsec - a.nsec);
 };