Your first Flusspferd program

Previous: Using Flusspferd from C++

Let's begin with a very simple program, a version of "Hello World".

#include <flusspferd.hpp>
#include <iostream>
#include <ostream>

int main() {
    // Create and use a context, needed to be able to use Flusspferd.
    flusspferd::current_context_scope context_scope(
        flusspferd::context::create());

    // Create a new string and protect it from the garbage collector by making
    // it a root string.
    flusspferd::root_string str("Hello, World!\n");

    // Demonstrate that str will not be garbage collected, by calling the
    // garbage collector.
    // Note that there is no other reason to call the garbage collector here.
    flusspferd::gc();

    // Set a property on the global object. Effectively, this creates a global
    // variable "str" with the contents of str.
    flusspferd::global().set_property("str", str);

    // Print str on std::cout - but first, replace "World" by "Flusspferd".
    std::cout << flusspferd::evaluate("str.replace('World', 'Flusspferd')");
}

Note:

You can find the source file listed above in help/examples/first_program.cpp.

In order to use Flusspferd, we need to create a context and make it the current context, which flusspferd::current_context_scope does as long it is in scope. You can use flusspferd::current_context_scope in multiple nested scopes.

Compiling Flusspferd in your project

Now that you've got a (very) simple project that uses Flusspferd, its time to compile it.

We assume that you have already installed Flusspferd. To use it in your project, you can use pkg-config, like this:

$ g++ $(pkg-config --cflags --libs flusspferd) myfile.cpp

If you use a build system, you can use its pkg-config integration.

Let's go with the simple method of shelling out to pkg-config for now. We don't recommend that you use this method for any serious development, but it has the advantage of being easy and quick.

$ g++  $(pkg-config --cflags --libs flusspferd) -o first_program first_program.cpp >/dev/null
$ ./first_programm
Hello, Flusspferd!
$

If you see the output "Hello, Flusspferd!" and just get a shell back, then everything worked. If either of the above commands produces any different output, then something went wrong in the install proccess and most likely a required file couldn't be found.

Next: Values and objects.