A classic build-a-calculator project - this is the capstone for the Foundations course from The Odin Project.
The project description is pretty light on requirements for calculator performance beyond the basics. I decided to write my own spec here as I figured it would be helpfull to write out longhand what a basic calculator actually needs to do.
The calculator screen needs to display a numerical string up to a known length.
The calculator needs keys:
- Num keys (0-9 plus a point sign)
- Function keys (clear, plus/minus, and percent)
- Operator keys (+, -, *, /)
- Equals key
Logic run by the calculator is triggered on key press.
- Tapping num keys updates the number displayed on a screen
- if the displayed number is the returned result from the last calculation, it is overwritten
- Tapping an operator sets that for the next calculation, saving the displayed value as the first, and subsequent num inputs will be stored ready for calculation
- Tapping the equals key runs a calculation
- if there is only one number value it runs that number as both sides of the operation
- if there is a previous returned value, the calculation runs with the returned value as the first argument, and the old second value as the second argument
- Tapping the clear key deletes the current displayed value, and tapping it again delete a previous value if that exists
- Tapping the plus-minus sign or percent sign inverts the displayed number, or divides the displayed number by 100 respectively.
I have decided to extend the project to a build the interface in the style-de-jour: the Teenage Engineering EP–133 K.O. II Sampler
I was particularly motivated by seeing the gorgeous button design by Noah Shreve seen below.
This image will be used as my design spec as there is no public Figma or Sketch file available.
