Filter input

[meisenzahl]

Resolves #133

[meisenzahl]

On keyboard input % is not accepted as valid input and a warning is shown.

Should the input using the % button still be possible or should the button be removed?

Referring to discussion in #44 with reference to https://speedcrunch.org/userguide/syntax.html#deprecated-operators.

[jeremypw]

Thanks for you first contribution to Calculator!
As you mention the question of the % button (which still works and still can give rise to an ambiguous calculation) is outstanding.
A simple solution to the % button is to cause it to complete any pending calculation first and then apply the % operation (i.e. divide by 100). That way you never see the % entered into the pending calculation.

It seems shame that there is no quick way to increase (or decrease) a number by x% though. I guess that can be fixed in another PR if agreement can be found on how to do it. Maybe by allowing a +% operator, so 50 +% 10 = 55.

I've proposed one solution here: #137

[meisenzahl]

I'm closing this because I don't know how to proceed.