add isNaN and isFinite as native functions

libraries/Basics.elm

@@ -30,6 +30,9 @@ are your tuples so big?
 # Number Conversions
 @docs round, floor, ceiling, truncate, toFloat
 
+# Floating Point Checks
+@docs isNaN, isFinite
+
 # Angle Conversions
 All angle conversions result in “standard Elm angles”
 which happen to be radians.
@@ -271,6 +274,17 @@ ceiling = Native.Basics.ceiling
 toFloat : Int -> Float
 toFloat = Native.Basics.toFloat
 
+{- | Determines whether a float is an undefined or unrepresentable number,
+such as 0/0. NaN stands for *not a number*.
+-}
+isNaN : Float -> Bool
+isNaN = Native.Basics.isNaN
+
+{- | Determines whether a float is finite. Positive and negative infinity are
+valid floating point numbers, created by computations like `1/0` and `-1/0`.
+-}
+isFinite : Float -> Bool
+isFinite = Native.Basics.isFinite
 
 -- Function Helpers
 

libraries/Native/Basics.js

@@ -53,6 +53,8 @@ Elm.Native.Basics.make = function(elm) {
       floor:Math.floor,
       round:Math.round,
       toFloat:function(x) { return x; },
+      isNaN:isNaN,
+      isFinite:isFinite
   };
 
   return elm.Native.Basics.values = basics;