Our Friend Otto auto

Simplify declarations; examples...

auto err_val = PyList_New(2);

for (auto node: ast.nodes) {

auto distance = (ast.choice == 0 ? eval_real_number : eval_integer)(*ast.nodes[1]);

for (auto i = 1u; I < ast.nodes.size(); ++i) {

Decltype

Same purpose as typedef, ensure declarations have the same type, but sometimes more convenient, or better if the type isn't something you have direct control over:

            auto list_size = PySequence_Fast_GET_SIZE(models);
            for (decltype(list_size) i = 0; i < list_size; ++i)

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Initializer Lists

For initializing containers:

static std::vector<std::string> symbols = { "&", "|" };

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Raw Strings

For more easily specifying strings that have lots of special characters (think newlines and backslashes) such as regular expressions or parser grammars.

The basic syntax is:

R"(some complex string)"

Since in some situations the sequence )" might occur in the string, additional characters can be between the R and the ", e.g.:

R---"(some complex string)---"

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Humongous Lambdas

It just didn't occur to me that lambdas could be more than short anonymous functions handled off as arguments to other functions, e.g.:

    // as_term
    spec_parser["as_term"] = [](const SemanticValues &vs) {
        auto objects_inst = std::any_cast<PyObject*>(vs[0]);
        if (vs.choice() == 1) {
            // tilde
            auto ret = PyObject_CallMethodObjArgs(objects_inst, invert_arg, session, models, nullptr);
            if (ret == nullptr)
                throw std::logic_error(use_python_error);
            Py_DECREF(ret);
            outermost_inversion = true;
        } else
            outermost_inversion = false;
        if (vs.size() == 1)
            return objects_inst;

        // there's a zone selector
        return process_zone(std::any_cast<PyObject*>(vs[0]), vs[1]);
    };

Any type

Hold a copy of a value and its type.

#include <any>
#include <iostream>
#include <string>

int main() {
    std::any a; // Empty std::any

    a = 42; // Stores an int
    std::cout << "Value: " << std::any_cast<int>(a) << std::endl;

    a = "Hello, C++!"; // Stores a const char*
    std::cout << "Value: " << std::any_cast<const char*>(a) << std::endl;

    a = std::string("Dynamic string"); // Stores a std::string
    std::cout << "Value: " << std::any_cast<std::string>(a) << std::endl;

    try {
        // Attempting to cast to the wrong type will throw an exception
        std::cout << std::any_cast<double>(a) << std::endl;
    } catch (const std::bad_any_cast& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }

    return 0;
}

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