C++ Alternative OperatorsHome

Cursed C++: Alternative Operators

C++ alternative operators is a legacy feature that truly makes any codebase cursed.

%:include <iostream>

struct A <%
    A(int bitand a) : a(a) {}
    int bitand a;
%>;


int main(int argc, char**argv)
<%
    if(argc not_eq 2) <% return 1;%>

    int n = std::atoi(argv<:1:>);
    A a(n);

    auto func = <:bitand:>(A a)<%
        std::cout << a.a << std::endl;
    %>;

    func(a);
    return 0;
%>

You might not believe it, but this code compiles and prints the integer provided as an argument.

List of alternative operators

This is the list of alternative operators in C++.

Primary	Alternative
&&	and
&=	and_eq
&	bitand
|	bitor
~	compl
!	not
!=	not_eq
||	or
|=	or_eq
^	xor
^=	xor_eq
{	<%
}	%>
[	<:
]	:>
#	%:
##	%:%:

The most notable one is bitand which can hilariously be used to indicate a reference as shown in the example above.

What are these for?

C source code must be compatible with the ISO 646 invariant character set. This non-ascii character set was developed as a base for international 7-bit variant character sets. Due to C++ backwards compatibility with C, these alternative operators are also in C++ today.

ISO 646 invariant structure

The invariant character set has 34 control codes (characters such as NUL and DEL) and 82 non-control characters.

Here are the 82 non-control characters: !"%&'()*+,-./0123456789:;<=>?ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz

You might notice that these characters {}[] are missing. This is why alternative operators were added in C.

The invariant leaves 12 characters for international variants.

As an example of international use, this is how the french-canadian variant used its 12 spare characters: #$àâçêîôéùèû.

It is a bit mysterious why & needs an alternate operator when it is in the invariant. It appears that some international variants went beyond the 12 characters and replaced other characters like !. I could not find a specific variant replacing & but the ! character is supported with the not keyword in C++, leading me to believe that & is supported because there's a variant not using it.

Questions? Comments? Insults? Send me an email! moc.snetramcirdec@cirdec

Created: 2022-11-26 - Last Edited: 2022-11-26