The Escape button should be implemented to clear the cache.
This is not essential, but doesn't break the workflow while using the calculator via keyboard.

An example for explanation: [1][2][Start] -> produces "12,00" in the output.
Pressing a digit afterwards will reset the state and go on with a new number. E.g. pressing [1] will result in "1,"
Pressing an operator will use the shown value for the upcoming calculation. E.g. pressing [+][2][=] will result in "14,".

Now: What should the sign command do?
v1: Behave like an operator -> [(-)] -> "-12,00" -> [+][1][=] -> "-11,"
v2: Behave like a digit -> [(-)] -> "-0," -> [1] -> "-1"

I tried to make a regular division 144:12 but unfortunately without any result or error.
Other ones such as 150:10 are working.

v0.11

The internal calculations use double values rather than decimal ones. At the moment there is no need for decimals. But as the calculator evolves maybe decimals will be important.

Situation: When setting one of the financial values (Start, Rate etc.) the vm keeps track of them so that if 4 values are given the fifth is calculated immediatly after the corresponding command was pressed.

The error now is that the vm sets the Years flag also if only the rates per annum are set as a second function of the Years button.

Given all the other parameters (Years, Start, ...) and pressing the Interest button afterwards should calculate the nominal interest rate number, the effective interest rate number and should display the effective interest rate.

Instead it calculates the nominal interest rate (and displays it) and uses the nominal interest rate again to calculate another instance of the nominal interest rate instead of the effective interest rate.

Steps to reprodce:

• Activate second function (*)
• Click Start
• -> Label Advance is active and so is the internal flag for calculations
• Long press the clear buttun (C)
• -> expected result: Label Advance is unset (->true) and so is the internal flag for calculations (-> false, that is the problem)

If a control of the fincalc vm has the focus and a key is pressed it gets handled twice. The reason is that there are two handlers active. One from the shellview and one from the fincalc view.
Furthermore even if the user is on another view than the fincalc view the keyboard presses are still handled within the fincalc viewmodel. The reason is that the global handler in the shellview passes the keys via eventaggregation the every subscriber no matter which view is currently active.

Right like the hardware model, the usage should be more intuitive. Without reading the manual it is hard to discover how to enter values in the correct order and way.
Maybe it is is a good idea to have a look on other tools. There they clearly ask you which value are you looking for and which other ones are needed.
This is mainly a limit for the existing hardware calculator and not necessary for the software version.

Steps to reproduce:

• Enter a digit, say 5
• Press Rate button

Expected behavior:

• Display shows 5,00 and rate label text is active

Actual behaviour:

• Output text is set to 0, and rate label text is not active