Merge pull request #345 from sideeffffect/master

add getOrFailF function to Option

Author: forki

src/FSharpx.Extras/ComputationExpressions/Monad.fs

@@ -232,6 +232,12 @@ module Option =
         | Some x -> x
         | None -> failwith m
 
+    /// Gets the value associated with the option or print to a string buffer and raise an exception with the given result. Helper printers must return strings.
+    let inline getOrFailF fmt =
+        function
+        | Some x -> x
+        | None -> failwithf fmt
+
     /// Gets the value associated with the option or raises the supplied exception.
     let inline getOrRaise e =
         function