Operator overloading: implies, +=, *=...

[Toky Olivier Razanakotonarivo]

Hello,

Can you tell please how to implement operator overloading with += or *= operators? And can you tell what is “Implies” operator? There is no documentation about it if I’m not wrong.

Thank you so much.

[Eric Grange]

Hi,

”implies” was added in compatibility with RemObjects Oxygen, it checks for a mathematical implication, ie. “a implies b” is equivalent to “(not a) or b” ( https://www.delphitools.info/2011/01/19/leaps-and-bounds-of-dwscript/)

At the moment the combined assignement operators are not overloadable, back in the day when I looked at it there was an ambiguity on how they should handle properties, so they were left aside, and the issue got a bit buried since :/

The main ambiguity IIRC was whether

obj.prop += val;

should be treated as a custom implementation for the syntax sugar that '+=' is

obj.prop := obj.prop + val;

or as a method

obj.prop.plus_assign(val)

The syntax sugar is the most logical/least surprise one, but has issues when property getter/setter are involved (it really needs to be implemented a template in those cases to be truly beneficial, like its is in various C++ vector libraries).

The method approach is the one that made sense for things like using “+=” as an alternative to Add(), but makes very limited sense outside of those uses, so it was debatable if it did anything else than bring confusion.

I have not looked into the subject since, not sure if Embarcadero/FreePascal crowds made any decision there that could be followed.

[Toky Olivier Razanakotonarivo]

Hi,

Thank you for you response. I just asked if it there is a method to overload it or I did it wrongly but it if it’s the case, I will change my approach. So at this time, I can use them but cannot overload. Thank you.