One of the authors of the Qt Blog shared his experience of using the Cling utility. To solve everyday problems, he needed to write several scripts, and he used C ++ as a scripting language!!! To do this, he used the Cling utility, which is a C++ interpreter based on the Clang compiler and created by CERN.
Cling allows developers to write scripts using C and C++. Because it uses the Clang compiler, it supports the latest versions of the C++ standard. If you execute the interpreter directly, you will have a live runtime where you can start writing C++ code. As part of the standard C/C++ syntax, you'll find several other commands beginning with "." (Dot).
When you use the interactive interpreter, you can write code like:
- #include <stdio.h>
- printf("hello world\n");
As you can see, there is no need to worry about areas; you can just call the function.
If you are planning to use Cling as an interpreter for your scripts, you need to wrap everything inside a function. The default entry point of a script is the same as the filename. It can be configured to call a different function. So the previous example would turn into something like:
- #include <stdio.h>
- void _01_hello_world() {
- printf("foo\n");
- }
... or C ++ version
- #include <iostream>
- void _02_hello_world()
- {
- std::cout << "Hello world" << std::endl;
- }
The examples are pretty simple, but they show you where to start.
What about Qt?
- #include <QtWidgets/qapplication.h>
- #include <QtWidgets/qpushbutton.h>
- void _03_basic_qt()
- {
- int argc = 0;
- QApplication app(argc, nullptr);
- QPushButton button("Hello world");
- QObject::connect(&button, &QPushButton::pressed, &app, &QApplication::quit);
- button.show();
- app.exec();
- }
But this code won't work out of the box - you need to pass some custom parameters to Cling:
- cling -I/usr/include/x86_64-linux-gnu/qt5 -fPIC -lQt5Widgets 03_basic_qt.cpp
You can customize your "cling" in a custom script based on your needs.
You can also download Cling as a library in your applications to use C++ as a scripting language.
