Riddle

Tiny Scripting Language

A very basic scripting language implemented in C++.

• Python-like indentation and syntax
• Very small programs; global, argument, and stack indices expressed in one byte.
• Native types are directly implemented with bool, long, std::string, std::vector<riddle::Val> and std::map<riddle::Val,riddle::Val>.
• Most other C++ values can be understood by a script out of the box.

Install

Run make install to install:

• headers are copied to $(PREFIX)$(includedir)/riddle/
  • by default $(HOME)/.local/include/riddle/
• the library is copied to $(PREFIX)$(libdir)
  • by default $(HOME)/.local/lib

You can remove the installed files with make uninstall.

Usage

A C++ program can use Riddle by linking with either libriddle.a or libriddle.so and including riddle/riddle.hh.

To use Riddle you first create a global scope where values and functions are exported. Riddle does not provide any function beyond basic operators, so you need to provide anything that the users can require:

    riddle::Scope global;
    global.add("print", riddle::Val(&fun_print_));
    global.add("scan", riddle::Val(&fun_scan_));
    global.add("type", riddle::Val(riddle::make_fun(&fun_type_)));
    ...

If you want to execute some Riddle code stored in a plain string, you can use the riddle::eval() function as follows:

    try {
            std::cout << riddle::eval(global, TEXT) << "\n";
    } catch (std::exception& ex) {
            std::cerr << ex.what() << "\n";
    }

If you want to compile some Riddle code and then call it repeated times, you want to do this instead:

    riddle::Standalone snippet{global, TEXT};
    try {
            std::cout << snippet(ARGS, ARGN) << "\n";
    } catch (std::exception& ex) {
            std::cerr << ex.what() << "\n";
    }

And if you want to run an interactive shell where the user can store additional values in a context and every line that's run is discarded you can do this:

    riddle::Interactive interactive{global, ARGS, ARGN};
    while (READ NEW LINE) {
            try {
                    std::cout << interactive(LINE) << "\n";
            } catch (std::exception& ex) {
                    std::cerr << ex.what() << "\n";
            }
    }