Use modulo instead of remainder for even?/odd?.

Works better for negative and fractional numbers.

2 files changed, 24 insertions, 2 deletions

diff --git a/src/boot/boot.janet b/src/boot/boot.janet
index 0a677370..4ddbbef2 100644
--- a/src/boot/boot.janet
+++ b/src/boot/boot.janet
@@ -79,8 +79,8 @@
 
 # Basic predicates
 (defn nan? "Check if x is NaN" [x] (not= x x))
-(defn even? "Check if x is even." [x] (= 0 (% x 2)))
-(defn odd? "Check if x is odd." [x] (not= 0 (% x 2)))
+(defn even? "Check if x is even." [x] (= 0 (mod x 2)))
+(defn odd? "Check if x is odd." [x] (= 1 (mod x 2)))
 (defn zero? "Check if x is zero." [x] (= x 0))
 (defn pos? "Check if x is greater than 0." [x] (> x 0))
 (defn neg? "Check if x is less than 0." [x] (< x 0))
diff --git a/test/suite1.janet b/test/suite1.janet
index 5b9f4f4f..c3d625d6 100644
--- a/test/suite1.janet
+++ b/test/suite1.janet
@@ -259,4 +259,26 @@
 (assert (array= (array/slice @[1 2 3] 0 2) @[1 2]) "array/slice 1")
 (assert (array= (array/slice @[0 7 3 9 1 4] 2 -2) @[3 9 1]) "array/slice 2")
 
+# Even and odd
+
+(assert (odd? 9) "odd? 1")
+(assert (odd? -9) "odd? 2")
+(assert (not (odd? 10)) "odd? 3")
+(assert (not (odd? 0)) "odd? 4")
+(assert (not (odd? -10)) "odd? 5")
+(assert (not (odd? 1.1)) "odd? 6")
+(assert (not (odd? -0.1)) "odd? 7")
+(assert (not (odd? -1.1)) "odd? 8")
+(assert (not (odd? -1.6)) "odd? 9")
+
+(assert (even? 10) "even? 1")
+(assert (even? -10) "even? 2")
+(assert (even? 0) "even? 3")
+(assert (not (even? 9)) "even? 4")
+(assert (not (even? -9)) "even? 5")
+(assert (not (even? 0.1)) "even? 6")
+(assert (not (even? -0.1)) "even? 7")
+(assert (not (even? -10.1)) "even? 8")
+(assert (not (even? -10.6)) "even? 9")
+
 (end-suite)