SleepyToDeath / rubify

Write C++ like Ruby

Rubify

C++ is great and powerful, but lacks some very basic functions like string.split, vector.group_by, etc. This library allows you to write them in C++ like in Ruby. Syntactic sugar is sweeeet!

It's basically a wrapper for std::string and some containers, extending them with the functionality of their counterpart in Ruby.

I'm conservative and trying to stay compatible with native C++. For example, elements are not assumed to always be pointers, and there's no universal parent type "Object".

In addition, there are some experimental features that I find useful but not necessarily supported by Ruby, such as do_once, Algebraic Effects, etc.

Examples

See test.cpp.

Dependency

If you don't use Algebraic Effects: A compiler that supports C++11

If you use Algebraic Effects: A compiler that supports C++2a (for type deduction)

Installation

Drop it anywhere in your PATH. Include rubify.hpp. Add rubify.cpp to your source file for compiling.

Coding Conventions

Containers

Rubify::string derives std::string, and is equivalence of String in Ruby.

Rubify::vector derives std::vector, and is equivalence of Array in Ruby.

Rubify::map derives std::map, and is equivalence of Hash in Ruby.

C++ lambda is equivalence of block in Ruby.

Member functions

If the std container already has a function, (e.g., push_back), it won't be overridden(e.g. by append). Otherwise, the function name and behavior will be the same as in Ruby(if possible). ! character is not allowed in C++ as identifier, so it's replaced by _ (underscore). ? is not allowed either. But it incurs no ambiguity. So it's simply removed.

Container elements are copied by value, unlike in Ruby, where everything is an object. If you want things to work the Ruby way, pass around pointers for everything.

Types can't be mixed up in a container, nor can elements' type be changed(e.g. by map_), unless you define everything as subtype of an "Object" class like in Ruby.

To break or continue the iteration within a lambda, break and continue won't work. Use break_ and continue_ instead. Currently only supported in each. Usage in other situations will cause an exception.

String interpolation

A macro _S_ is defined for string interpolation. _S_( exp ) will evaluate exp and turn the result into a string. exp's result type must either has to_s() function defined or can be fed to stringstream.
If you are too lazy to type the surrounding + symbol, use S_ instead.
An example:
a = 1;
b = 2;
cout << "" S_(a) " plus " S_(b) " equals " S_(a+b) "" << endl;
Output:
1 plus 2 equals 3

You can undefine puts if it's useless for you.

Algebraic Effects

I'm actually not a super fan of FP. My knowledge about this mechanism mainly comes from this article. And here is a Chinese translation. I recommend reading the article for a better understanding of it.

There are 2 keywords in my implementation: require_ and provide_. require_ is like throw. It throws a requirement that can be caught by provide_ block (similar to catch). The interface require_(Want, name) throws a requirement with return type of Want. name is literally the name of the required thing. It can be of any type.

provide_(handler) can catch a requirement and feed it to handler, which is a function pointer or a lambda. After calling require_(Want, name), the first handler up in the stack that accepts name (type must be the same) and returns a value of Want type will catch the thrown requirement. If the requirement can be handled, the program will jump back to the place require_ is called and replace the statement with the return value. Otherwise the handler can call return require_(Want, name); to throw the requirement again to upper levels. If no handler in the stack can handle it, name will be thrown as an exception.

Both operations are thread safe. Each thread is provided with its own context. When a new thread is created, nothing is derived from the parent thread and the initial stack is empty. If you want to require something from another thread (e.g. worker from master), use require_from_(thread_id, Want, name) and the other thread's current context will be used. This may be dangerous, so be careful with it.

One example can be found in test.cpp where a recursive function dive into multiple levels and require a value provided by an upper level from the bottom.

Tips

Read comments in real_rubify.hpp for more details.

Some tips on using C++ if you've never used C++11 or later:

A lambda is essentially a function pointer, but can optionally capture local context. The most brainless way to define a lambda is like this:
[&]( $arguments ) -> $return_type {
$body
}
It captures all local contexts and should work in most cases.

Try to use auto feature in C++. It saves you a lot of effort figuring out and typing the proper type name.
For example: auto add = [&](int a, int b) -> int {
return a+b;
};
auto c = add(1, 2);

Supported Functions

String interpolation

• S_
• _S_

Short circuit

• continue_
• break_

vector:

• [] (support negative index)
• +
• +=
• &
• *
• take
• drop
• each (with/without index)
• group_by
• sort_by
• sort_by_
• map (with/without index)
• map_ (with/without index)
• select
• select_
• zip
• norm_zip (duplicate the shorter vector's elements to make them equally long, then zip)
• flatten
• to_s
• join
• to_h

string:

• < (comparison)
• split

map:

• each
• to_a
• to_s

Algebraic effects

• provide_
• require_

Helper functions

• do_once
• do_a_few_times
• do_at_interval
• do_a_few_times_at_interval

TODO:

• more functions
• Enumerator
• conversion between types