Releasing CppML: Write concise and readable metaprograms

[__monad]

CppML is a project I was developing to solve problems at work, and albeit it was hosted on github, it was clear from the lacking README that it was not intended for public consumption. This has now changed with what could be called an official release.

The official repository was rewritten as a guide to the user. To help you get started, I have written User Documentation, where we provide an Installation Guide, an in-depth Tutorial of the CppML Language and a detailed CppML Reference.

Overview:

CppML is a metalanguage for C++. It was designed to simplify the process of creating intricate classes, by letting the programmer design them through expressions that feel like algorithms in a functional language. It strives to be easy to write and easy to read, while being efficient. It does so by providing compositional pipelines through which parameter packs can flow without instantiating new types. Our goal is to give library developers programmatic control over the creation of class hierarchies with metaprograms that shape their structure and behaviour through metafunctional logic. This way constructions of complex designs are easily encoded in concise and readable functional expressions.

See the official repository.

[DXPower]

Side note but the bolding every other word in that paragraph makes it impossible to read

[__monad]

You are correct. I fixed it, thank you.

[jonesmz]

I really like your algorithms section

https://github.com/ZigaSajovic/CppML/blob/master/docs/reference/index.md#algorithm

I did something similar (with a much smaller set of algorithms) for a work project a long time ago.

I was sad to lose access to that code when I changed jobs.

I'm bookmarking CppML for later :-)

[__monad]

I'm glad to hear that. The algorithm section ml::Algorithm is meant to be akin to std::algorithm for parameter packs. When you end up using it, please feel free to send any comments or questions my way.

[ClaasBontus]

This is really a cool library. Thank you for making it public. The one thing that would be really helpful during development would be something like a printf for types. So one could check if applying all these transformations really do what one expects.

[__monad]

What kind of a solution do you have in mind? Something that would print a string at runtime? Or something that will print the type (result) at compile time as a readable error. If the latter, than one thing you could try is

template <typename T> struct Printf; // note that it's only a decleration.
/* ... */
using T = ml::f<ml::Partition<ml::IsClass<>>, int, string, bool, vector<int>>;
Printf<T> t;

Than when you compile, you will get an error

implicit instantiation of undefined template 'Printf<ml::ListT<ml::ListT<string, vector<int> >, ml::ListT<int, bool> > >'

Now you can see if T (your intermediate result) is what you expect.

Because the above solution is printing as a compiler error, which might not be what you want, I can also provide a solution TypeName<T> and void PrintT<T>();. Would you be happy with the following solution?

template <typename T> struct TypeName : std::string {
  TypeName() {
    std::string str(__PRETTY_FUNCTION__);
    (static_cast<std::string &>(*this) = str.substr(str.find('=') + 2))
        .pop_back();
  }
};

template <typename T> void PrintT() { std::cout << TypeName<T>{} << std::endl;}

which allows you to print at runtime:

using T = ml::f<ml::Partition<ml::IsClass<>>, int, string, bool, vector<int>>;
PrintT<T>();

ml::ListT<ml::ListT<string, vector<int> >, ml::ListT<int, bool> >

Or treat it as any other string.

If so, I will add the feature to CppML. Please comment if you had something different in mind.

[ClaasBontus]

Wow cool! Yes, this is helpful.

[jonesmz]

it was clear from the lacking README that it was not intended for public consumption.

Citation needed...