An `encapsulated` type is one that has no public data members.

A `noncopyable` type is one that has no user-defined copy or move functions (`operator=` with `this` and `that` parameters).

A `singleton` type is one that has only one global object (instance) in the whole program. The single object is initialized lazily the first time it is accessed. A singleton type has no constructors other than a generated default constructor (note: therefore all data members must have default values), and provides a generated `instance()` function to create and give access to the global instance.

For example:

``` cpp title="A templated custom safe union type" hl_lines="1 7"

my_singleton: @singleton type = {

value: int = 42;

print: (this) = std::cout << "(value)$\n";

}

main: () = {

my_singleton::instance().print();

}

An `autodiff` type is extended so that derivatives can be computed. The metafunction adds for each function and member function a differentiated version. **This is a proof of concept implementation. Expect it to break.**

A simple hello diff example is:

``` cpp

ad: @autodiff type = {

func: (x: double) -> (r: double) = {

r = x * x;

test: @singleton type = {

value: int = 42;

print: (this) = std::cout << "(value)$\n";

}

main: () = {

test::instance().print();

}

42

42

let count=count+1

printf "[%s] Starting gcc 10 %s\n" "$count" "$f"

g++-10 -I../../../include -std=c++20 -pthread -Wold-style-cast -Wunused-parameter -Wno-unused-result -o test.exe $f > $f.output 2>&1

rm -f $f

if test -f "test.exe"; then

let exe_count=exe_count+1

42

let count=count+1

printf "[%s] Starting gcc 14 %s\n" "$count" "$f"

g++ -I../../../include -std=c++2b -pthread -Wold-style-cast -Wunused-parameter -Wno-unused-result -o test.exe $f > $f.output 2>&1

rm -f $f

if test -f "test.exe"; then

let exe_count=exe_count+1

Microsoft (R) C/C++ Optimizing Compiler Version 19.50.35721 for x64

Copyright (C) Microsoft Corporation. All rights reserved.

42