Added odd/even functions

1 files changed, 20 insertions, 0 deletions

diff --git a/std/Number/Ternary.bruijn b/std/Number/Ternary.bruijn
index dfed84c..7ebb978 100644
--- a/std/Number/Ternary.bruijn
+++ b/std/Number/Ternary.bruijn
@@ -435,6 +435,26 @@ mod ~‣ ∘∘ quot-rem ⧗ Number → Number
 
 …%… mod
 
+# returns true if the number is even (remainder mod 2 == 0)
+# TODO: faster solution (using tupling?)
+even? z [[rec]]
+	rec =?0 case-end case-rec
+		case-rec t⁰? (lst 0) (1 /³0) ¬(1 /³0)
+		case-end true
+
+:test (even? (+0)) (true)
+:test (even? (+1)) (false)
+:test (even? (+41)) (false)
+:test (even? (+42)) (true)
+
+# returns true if the number is odd (remainder mod 2 == 1)
+odd? ¬‣ ∘ even?
+
+:test (odd? (+0)) (false)
+:test (odd? (+1)) (true)
+:test (odd? (+41)) (true)
+:test (odd? (+42)) (false)
+
 # returns max number of two
 max [[(1 ≤? 0) 0 1]] ⧗ Number → Number → Number