This is a calculator keyboard made to easily compute math equations in any program just by opening your keyboard. This is a immediate execution calculator, much like the stock iOS keyboad on iPhones, so the user presses a key for each operation, by pressing operation keys to calculate all the intermediate results, before the final value is shown. Once the user has calculated the result they want, they are able to insert it where the cursor is curently located.
This is my first custom iOS custom keyboard, a feature enabled in iOS 8. I used Xcode 7 and swift 2.0 for developing along with Sketch for designing the layout.