proxy

Class template `operator_dispatch`

The definition of operator_dispatch makes use of an exposition-only type string-literal, which is constructible from a char array at compile-time and can be used as a non-type template argument.

template <string-literal Sign, bool Rhs = false>
class operator_dispatch;

Class template operator_dispatch is a dispatch type for operator expressions. Sign represents the sign of operator (SOP) as a string literal (e.g., "+" for operator +). Rhs specifies whether the proxy operand is on the right-hand side of a binary operator.

Supported SOPs

As per C++20 specifications, there are 44 different SOPs. operator_dispatch supports the following 36 SOPs:

"+", "-", "*", "/", "%", "++", "--", "==", "!=", ">", "<", ">=", "<=", "<=>", "!", "&&", "||", "~", "&", "|", "^", "<<", ">>", "+=", "-=", "*=", "/=", "&=", "|=", "^=", "<<=", ">>=", ",", "->*", "()", "[]"

The following 8 SOPs are not supported:

new, new[], delete, delete[], and co_await are context-dependent and not applicable for proxy.
Assignment (=) and indirection (->) are ambiguous in the context of proxy.
Literals ("") apply only to a limited number of primitive types and are not applicable for proxy.

Type Conversion

Type conversion expressions, although using operator syntax, do not have a specific sign and are not within the scope of operator_dispatch. They are supported by another class template conversion_dispatch.

Specializations

Let self be the operand of proxy, and other and others... be the other operand(s) in the expression of an operator. operator_dispatch has the following specializations for various expressions:

Specializations	Expressions
`operator_dispatch<"+", false>`	`+self`, `self + other`
`operator_dispatch<"-", false>`	`-self`, `self - other`
`operator_dispatch<"*", false>`	`self`, `self other`
`operator_dispatch<"/", false>`	`self / other`
`operator_dispatch<"%", false>`	`self % other`
`operator_dispatch<"++", false>`	`++self`, `self++`
`operator_dispatch<"--", false>`	`--self`, `self--`
`operator_dispatch<"==", false>`	`self == other`
`operator_dispatch<"!=", false>`	`self != other`
`operator_dispatch<">", false>`	`self > other`
`operator_dispatch<"<", false>`	`self < other`
`operator_dispatch<">=", false>`	`self >= other`
`operator_dispatch<"<=", false>`	`self <= other`
`operator_dispatch<"<=>", false>`	`self <=> other`
`operator_dispatch<"!", false>`	`!self`
`operator_dispatch<"&&", false>`	`self && other`
`operator_dispatch<"\|\|", false>`	`self \|\| other`
`operator_dispatch<"~", false>`	`!self`
`operator_dispatch<"&", false>`	`&self`, `self & other`
`operator_dispatch<"\|", false>`	`self \| other`
`operator_dispatch<"^", false>`	`self ^ other`
`operator_dispatch<"<<", false>`	`self << other`
`operator_dispatch<">>", false>`	`self >> other`
`operator_dispatch<"+=", false>`	`self += other`
`operator_dispatch<"-=", false>`	`self -= other`
`operator_dispatch<"*=", false>`	`self *= other`
`operator_dispatch<"/=", false>`	`self /= other`
`operator_dispatch<"&=", false>`	`self &= other`
`operator_dispatch<"\|=", false>`	`self \|= other`
`operator_dispatch<"^=", false>`	`self ^= other`
`operator_dispatch<"<<=", false>`	`self <<= other`
`operator_dispatch<">>=", false>`	`self >>= other`
`operator_dispatch<",", false>`	`self, other`
`operator_dispatch<"->*", false>`	`self ->* other`
`operator_dispatch<"()", false>`	`self(others...)`
`operator_dispatch<"[]", false>`	`self[other]` (until C++23) `self[others...]` (since C++23)
`operator_dispatch<"+", true>`	`other + self`
`operator_dispatch<"-", true>`	`other - self`
`operator_dispatch<"*", true>`	`other * self`
`operator_dispatch<"/", true>`	`other / self`
`operator_dispatch<"%", true>`	`other % self`
`operator_dispatch<"==", true>`	`other == self`
`operator_dispatch<"!=", true>`	`other != self`
`operator_dispatch<">", true>`	`other > self`
`operator_dispatch<"<", true>`	`other < self`
`operator_dispatch<">=", true>`	`other >= self`
`operator_dispatch<"<=", true>`	`other <= self`
`operator_dispatch<"<=>", true>`	`other <=> self`
`operator_dispatch<"&&", true>`	`other && self`
`operator_dispatch<"\|\|", true>`	`other \|\| self`
`operator_dispatch<"&", true>`	`other & self`
`operator_dispatch<"\|", true>`	`other \| self`
`operator_dispatch<"^", true>`	`other ^ self`
`operator_dispatch<"<<", true>`	`other << self`
`operator_dispatch<">>", true>`	`other >> self`
`operator_dispatch<"+=", true>`	`other += self`
`operator_dispatch<"-=", true>`	`other -= self`
`operator_dispatch<"*=", true>`	`other *= self`
`operator_dispatch<"/=", true>`	`other /= self`
`operator_dispatch<"&=", true>`	`other &= self`
`operator_dispatch<"\|=", true>`	`other \|= self`
`operator_dispatch<"^=", true>`	`other ^= self`
`operator_dispatch<"<<=", true>`	`other <<= self`
`operator_dispatch<">>=", true>`	`other >>= self`
`operator_dispatch<",", true>`	`other, self`
`operator_dispatch<"->*", true>`	`other ->* self`

Member Functions

Name	Description
(constructor) [trivial]	constructs an `operator_dispatch` object
`operator()`	invokes the dispatch

Member Types

Name	Description
`accessor`	provides accessibility to `proxy`

Example

#include <iomanip>
#include <iostream>
#include <numbers>

#include "proxy.h"

struct Number : pro::facade_builder
    ::add_convention<pro::operator_dispatch<"*=">, void(int)>
    ::add_convention<pro::operator_dispatch<"<<", true>, std::ostream&(std::ostream&) const&>
    ::build {};

int main() {
  pro::proxy<Number> p1 = pro::make_proxy<Number>(std::numbers::pi);
  *p1 *= 3;
  std::cout << std::setprecision(10) << *p1 << "\n";  // Prints: 9.424777961

  pro::proxy<Number> p2 = pro::make_proxy<Number>(10);
  *p2 *= 5;
  std::cout << *p2 << "\n";  // Prints: 50
}