Add basic vector functions to Util

src/Util.md

@@ -22,3 +22,26 @@ Applies a function to the contents of a `Left` if the value of the given `Either
   mapLeft f (Left x) = Left (f x)
   mapLeft f (Right x) = Right x
 ```
+## Vectors
+
+Define some operations for pairs of numbers, treating them roughly like vectors
+
+### Addition and Subtraction
+
+<!-- idris
+export infixl 8 >+<
+export infixl 8 >-<
+
+namespace Pair
+-->
+
+```idris
+  public export
+  (>+<) : Num a => (x, y : (a, a)) -> (a, a)
+  (x_1, x_2) >+< (y_1, y_2) = (x_1 + y_1, x_2 + y_2)
+
+  public export
+  (>-<) : Neg a => (x, y : (a, a)) -> (a, a)
+  (x_1, x_2) >-< (y_1, y_2) = (x_1 - y_1, x_2 - y_2)
+```
+