Re: Simulating new user-defined operators

Vidar Hasfjord wrote:
> In C++ you cannot declare new user-defined operators, i.e. it is
> impossible to define a new operator token with a specified precedent
> and meaning, e.g. the euro symbol (EURO) to convert a value into euro
> cents.
> 
> It is possible to simulate this to some degree using an object of a
> user-defined class with an operator overload. For example, with an
> "operator" object named E with a operator % overload, we can write (E%
> v) to mean some operation on v.
> 
> I've found great utility for this idiom in two areas: error code
> checking and resource string loading (internationalisation). For
> example, with E% as a error-check operator and SL% as a string load
> operator I can write:
> 
>    E%DeleteFile (file); // throws on error
> 
> and
> 
>    string caption = SL%IDS_VALIDATION_ERROR; // i18n
>    string message = format (SL%IDS_OUT_OF_RANGE) % value;
>    MessageBox (message, caption);
> 
> While I think such operator use may be considered obfuscation in the
> general case, I think it has merits when it forms an idiom used in
> large parts of the code. But would this code pass your code review?
> Opinions welcome.
> 

What are the merits of this solution over just using a set for ctors for
the E and SL cl*****?
E(DeleteFile(file));
string message = format (SL(IDS_OUT_OF_RANGE)) % value;

br,
Martin

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