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Clang Plays Tetris -- Tetris As a C++ Template Metaprogram
New submitter mjvzb writes: Ever wish compiling was more fun? Well, I recently implemented Tetris as a C++ template metaprogram (code at Github). The game is played by recompiling its source, taking player input by compiler flag. The runtime program is only needed to print the game screen to the console and save the game state across compiler runs.
Implementing Tetris in templates is not as horrific as you may imagine, and I've put together a post covering the details. Once you get over the syntax, C++ metaprogramming is just like functional programming.
Implementing Tetris in templates is not as horrific as you may imagine, and I've put together a post covering the details. Once you get over the syntax, C++ metaprogramming is just like functional programming.
Say what?
About semi-complex programs ending up re-implementing aspects of lisp or smalltalk-- just less elegantly.
I think you've done it!
This is proof as to exactly why C++ is such an abomination. I prefer languages that encourage elegant designs.
Nonfunctional programming is not really a different paradigm.
Who are you to judge that? Maybe he was lost in the depths of suicidal depression, and this project gave him a reason to drag himself out of it. Maybe an alien race will visit the earth and think that this is just so goddamn clever that there's no reason not to share their hyperdrive tech with us. Or whatever. But basically, fuck you and don't worry about what other people choose to do or not do.
He presumably means "just like" in the same sense as in the phrase, "Eating a high end steak dinner is just like having someone saw through your kneecaps with a circular saw".
Once you get over the syntax, C++ metaprogramming is just like functional programming.
No, the syntax is the entire thing wrong with C++ metaprogramming. It clearly wasn't designed for things like this. To clear up any doubt about the syntax, check out this file. In addition the inscrutable error messages (although those have improved over the past decade). If anyone likes template metaprogramming, I suggest they just use LISP.
That said, this project is really cool. Nice hack mattbierner.
"First they came for the slanderers and i said nothing."
metaprogramming is like functional programming in these senses:
1) Uses lots of recusion
2) Has no variables, only constants. Nothing is mutable.
3) Has functions
Because of 1 and 2, it helps to think in terms of functional programming if you want to do anything substantial.
"First they came for the slanderers and i said nothing."
If only the people who want to take on challenges like this put their skills to something actually useful....... There has GOT to be a better use of your knowledge and skills.
Sometimes people do things for fun........not because they want to please internet critics.
"First they came for the slanderers and i said nothing."
I am mystified how people can read this and not realize it was just a little fun thing to do in his spare time. Or do you spend every waking minute of your life doing serious things with your knowledge and skills?
"Old man yells at systemd"
I thought Tetris issued cease and desist letters for any implementation of its game, even if only for educational purposes.
When people find skills they are jealous of, they often try to discourage it and cover it up with phrases like:
* Don't you have a life?
* What a nerd
* You have too much time on your hands
* There has GOT to be a better use of your knowledge and skills
* There's something wrong with you
Ignore those critics and do what you want anyway. Your life will be better for it.
"First they came for the slanderers and i said nothing."
No, I don't wish compiling were more "fun". Like taking out the trash, or pruning my rose bushes, I want compiling to be over and done with as soon as possible so that I can get on with solving problems.
I especially don't want to have to BE a compiler writer, or try to divine the twisted mind of a compiler writer to solve problems. But that is exactly what you have to be, and how you have to think to use C++.
Which is why I won't touch it with a 10 foot pole.
Terrible language, desperately grasping for relevance in a world that passed it by long ago.
If you want functional programming, USE A FUNCTIONAL PROGRAMMING LANGUAGE.
When I had a $100 steak in Las Vegas, it melted like butter in my mouth. I don't think taking a circular saw to your kneecaps has the same pleasant experience.
Oh goody. So it's no different than any other monadic polymorphized differential functor system utilizing monoidal categories and parameterized applicative type expressions.
Whew. Lucky me. I was worried about finding something to do over the holiday weekend.
Maw! Fire up the karma burner!
No, the most terrifying and ridiculous thing would be if it was rewritten in JavaScript which outputted Java source that piped C# source that then, when compiled and executed, outputted as an x86 ASM program that produced a PHP script.
The world's burning. Moped Jesus spotted on I50. Details at 11.
Say what?
Template metaprogramming is exactly functional programming.
Not only that, C++98 style was completely 100% pure with no mutabe state. You got recuursion and pattern matching (called [partial] specialisation). A class is essentially a function returning a type (well, multiple types) as internal typedefs. And as such functions are very much first class objects.
C++11 added some local mutable state. constexpr functions can now be evaluated at compile time. Those yielding an int can be used as template arguments.
SJW n. One who posts facts.
Reference: The Tetris Company's victory in court three years ago
That just just it. I remember Alexander Alexandrescu talking about such stupidity on Usenet in the mid90's. The code without a doubt is complex. slow and resource hogging since you use the compiler as an interpreter. Just a way of wasting watts ( the power it takes the computer to run ). No serious professional programmer would even try to attempt such a thing and there is really no reason to. It also flies in the face of things that Stroustrup and Sutter have been saying at conferences like CppCon2014 to keep things simple. I also remember Scott meyer making a joke about someone noticing the template system being turing complete.
C++ TMP is turing complete and has no state. So yes it is functional. The point is not to write games though, but to write better tuned library code. I can only guess at the illicit substances the person doing this was ingesting.
If only the people who want to take on challenges like this put their skills to something actually useful....... There has GOT to be a better use of your knowledge and skills.
Sometimes people do things for fun........not because they want to please internet critics.
Then why would they blog about it... and then submit an article to Slashdot describing and linking to their own god dam blog.
Ordinarily I would agree with you, but this Matt Bierner clown clearly wants the fame, so he should cop any criticism on the chin.
How complicated can you make a rube goldberg machine? That's what this is thing is, a hacker's rube goldberg machine. Stop being so serious dickwads.
This confused me so much, I concurrently shot in my shorts and threw up in my mouth.
Has no variables, only constants. Nothing is mutable.
And... this is the definition of functional programming (referential transparency). So yes - it actually really *just like* functional programming, because it *is* functional programming.
I've done that sort of metaprogramming. Years ago I wrote a compile-time Lisp interpreter. It's a HORRIBLE language.
Look, say you have some advanced feature. You could write a library in scheme - it will take you 1 day to a week.
You could write it in C++ templates. It will have a worse feature set than the scheme version, it will be much less readable (not that scheme is readable) and much harder to use. It will have unusable error messages. And a mockup version will take you months to write.
Getting your mockup embedded in Boost and working well with it will take the help of a bunch of experts and a two or three times as much work.
If you want it included in the Boost libraries, you'll need a couple years of work integrating it and getting it approved.
Horrible.
someone was asking for the luajit implementer, Mike Pall, to add copying data structures as something optimized by the compiler and he was told that not sharing structures was a "code smell"
Oh God. The implementer is so out of touch and focused on low level efficiency that he doesn't recognize the basics of reliable programming.
Some time ago Elon Musk went on a rant about AI's destroying us.
AI's I do not fear, but C++ templates... there he might have something.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
Nonsense.
No one should ever have to work with C++ metaprogramming in their work.
It should not be encouraged. It's a horrible dead end. Sadly it isn't the only dead end in computer science.
What the fuck is "metaprograming"?
Sometimes you have to ask yourself, just because I CAN do this ... SHOULD I do this?
No.
In this case, the answer is clearly no.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
The title of this article is a little misleading, as this program works fine with the latest release of gcc (5.1) as well...
[No changes, either to the program or the command-line are required, just use "g++" instead of "clang++".]
Presumably it will also work with any compiler that supports a recent-enough version of the C++ standard and its proposed updates (with the command-line options updated accordingly).
We live, as we dream -- alone....
This is the most terrifying and ridiculous thing I've seen in my entire life.
Americans have spent more than a trillion hours watching reality TV. That is far more terrifying and ridiculous than someone playing with a Turing-complete compiler meta-language.
No one should ever have to work with C++ metaprogramming in their work.
He wasn't working.
He was playing.
Then why would they blog about it... and then submit an article to Slashdot describing and linking to their own god dam blog.
Because other people like to see it, and it's really cool. Specifically, if you don't like this kind of thing, you shouldn't be on Slashdot. See also this.
"First they came for the slanderers and i said nothing."
Wow, you must hate programming, if you think it's about work.
"First they came for the slanderers and i said nothing."
Template metaprogramming is exactly functional programming.
I got enlightened when I realized that C++ template metaprogramming is actually writing Prolog with a funny syntax.
This is like "functional" programming about as much as playing hopscotch all the way to the next town is like taking the train.
No one should ever have to work with C++ metaprogramming in their work.
In your own words: nonsense.
Like all tools it requires skill and good taste to use. You can do stupid stuff with it, but then there isn't a language out there which doesn't let you make stupid design decisions.
SJW n. One who posts facts.
This is the most terrifying and ridiculous thing I've seen in my entire life.
If only the people who want to take on challenges like this put their skills to something actually useful....... There has GOT to be a better use of your knowledge and skills.
It is one of the first things people do in programming - building games. My son is on the verge of learning computing, and he wishes to build a few games. Once these simpler things are achieved, more complex things are easier to do by more people.
The first thing I did in programming (on a Commodore 64) was building a database. Pretty sure it wasn't remotely game-like :)
Yeah they should do something useful! Like for instance:
Come up with ways to spy on your fellow citizens
Come up with ways to efficiently kill your fellow citizens
Come up with ways to brainwash your fellow citizens into submission
Come up with ways to make a couple of your fellow citizens an extraordinary amount of money in the hopes they might toss you some scraps
There are all kinds of great jobs in the tech sector these days in america.
It's almost all template programming anyway, just at a lower level.
... there really shouldn't be any.
I think the whole template 'metaprogramming' mess can be implemented
very well and readably by normal functions. After all, the only real difference
is that stuff is (partially) evaluated at compile time.
'template double power(double x)' would transform into:
double power(double x, constexpr int N);
'template void swap(T& x, T& y)' would become: /* any type */&y) { // ...
void swap(/* any type */ &x,
assert_sametype(x, y);
assert_moveable(x);
}
etc.
Expanding the idea, things that should logically be possible but are illegal with
current template syntax become trivial, e.g. templatizing on non-integral constants.
Even user-defined types become first-class citizens:
template void f() becomes: void f(constexpr double x);
struct Rectangle { int w; int h; };
template void clip() -> void clip(constexpr Rectangle R);
BTW, variables are over-rated, everything should be const unless specified
otherwise (use mutable, for instance).
I hope I can prove my point sometimes by designing that language, :)
but I'd need time and money...
Metaprogramming is useful for real things. It allows to automate some code generation instead of weiting redundant code by hand, which is definitely a great thing.
Metaprogramming is wonderful. C++ templates are horrible.
"Captain, you're asking me to work with equipment which hardly very far ahead of stone knives and bearskins. " - Mr. Spock
I don't see why you can't have multistage compiling so that you can use the full power of (whatever language) at "compile" time.
You should be able to have mutable data structures at compile time.
You should be able to have tables and arrays.
And custom file and network io.
Security hole? Like running a bash script isn't a security hole.
Not any more horrible than any other pure functional programming language, and people tend to find those elegant more than horrible.
Pure functional programming is pretty horrible too.
Take the classic book, "numerical recipes in Fortran"
( http://apps.nrbook.com/fortran... ) and try to convert all of the routines in there to pure functional style with no mutable variables, structures, arrays and no non-recursive loops.
Big step backwards. It will be horrible, it will obscure the code and it will run slowly.
It's funny that computer science doesn't build on old successes. They had good computer languages for doing math going back to the 50s but the latest and greatest bullshit being pushed in academia can't even do what they did in the 50's well.
void foo(bool on) {
if(on){
#define FOO
} else {
#undef FOO
}
}