The current code to manage the clipboard only supports a subset of functions managed by the calculator, has some issues to parse them (many false positives or issues with locales due to the conversion to en-us format but ignoring that '.' and ',' can be used for other purposes in the original locale) and very complicated to maintain/add new features (sin, pin, square, etc..).

In order to simplify and make this function more robust, we should instead use a language parser, more suited to our needs.

My proposal would be to use a custom Lexer to support all the different number formats (hex, bin, dec, bin, dec with exponent, ...) and modes (standard, programmer, etc...) we support and use a LR parser to verify and generate the list of commands. This solution would have many advantages:

• very easy to add new operator whatever their types (binary, pre-unitary or post-unitary)
• the parser will generate the sequence of commands while verifying the text, easier to maintain
• no false positive possible

In my proto-PR, I used Bison, a GPL v3 tool but providing an explicit exception to allow the use of the generated code without license.

It already manages a variety of features not currently available:

sinus/cos/tan

** Power, square, cube ** (#299)

more sign operators

Binary operations: OR, NOT, AND, XOR

and fix some reported bugs:

• minus sign not correctly supported: minus a negative number isn't interpreted correctly in scientific mode #294
• minus sign + parenthesis The calculator doesn't support pasted texts with a minus sign before a parenthesis #343

Proto-PR available here

https://github.com/rudyhuyn/calculator/tree/AddExpressionParser

remaining:

• add unit tests
• it only supports 0;0 and 0;3 grouping for the moment