Now write a function to unroll the while loop to “optimize it for the compiler”
Is this typescript?
Could be Java.
Seems like normal js?
Js is Math.Random. and NextInt() is a java method.
bad but more chaotic
you want to be punk rock not blues or jazz
x = -i;
Do many languages let you do that? When it’s in front of a variable I would’ve expected it to be a subtraction operator only and you would need to do x = -1 * i;
In most languages I’ve seen - is both a unary negation operator and a subtraction operator depending on context. So it would negate an integer literal or a variable in this context.
Personally I would expect it to behave the same in front of a numeric literal and in front of a variable. I do think most languages do that, but I haven’t actually tested that many and could br wrong.
But of course – It’s just flipping around the
-=operator!That only works if x is already 0
If i is 10 and x is zero, yes, x -= i would have a value of -10. If x was 5 from something else previously, x-=i would end with an x value of -5.
I just tested it in PowerShell. Works fine
$i = 1 $x = -$i $xOutputs -1
Why would they not let you do that? I honestly don’t know a single language that wouldn’t let you do that. Same as basic math notation allows you to do that.
x = -i
is a totally valid mathematical equation.
It’s a valid mathematical notation, sure. But there is an implicit understanding that the - in this case is making a number negative rather than subtracting (or, an implicit subtraction from 0).
With the way negative numbers generally work in binary there would be much different ones and zeroes stored behind the scenes, so handling that would have to be pretty intentional.
That said, I did just try it in Java because that’s what I work in normally and I swear I had a gotcha with that. But it worked fine as far as I can tell.
x = (function(){ return 10 })Or something like that
What is the value of x in the Good example before the loop?
Doesn’t matter, it’s 10 after the loop.
An int. Value doesn’t matter because it’s overwritten.
Not in this case. First, i is declared and assigned a value of 0. Next, x is declared and assigned a value of -i or -0. On the first loop iteration, i will decrement to -1, perform the conditional check, then execute the loop body which will assign x to -i or -(-1) or positive 1, and so on.
The only time a variable is created without a value is if you declare one without assigning a value like with
[int]i;
I know. OP asked what x was before the loop, and I just said it’s an int. The int can be any value because as you pointed out it will be set to 0 in the first loop iteration.
Shit, you’re right. x is declared inside the loop, so it doesn’t exist until the loop begins execution.
Technically, I suppose you could say the compiler will allocate memory for x without assigning a value before the loop is executed and… I’m understanding what you mean now, I think.
The code seems to be C-style language with curly braces and types in front for variable declarations, probably java. This means the variable must be declared of screen before the loop or it would not compile. It could have a previous value or be uninitialized, but that does not affect the end result.
I read in on C but it’s also true for JavaScript. The code implies that x was declared as an int sometime previously, or if JavaScript, just an object if not assigned a value giving it a type.
Yeah, it does look like C now that I think about it. You’re right about the end result too. I believe C# will let you do inline declaration and assignment like that, so maybe that’s what we’re looking at? Been a while, could be wrong
If this is JavaScript, it would have a value of -0, which is actually valid and works the same as normal zero thanks to type coercion. I think the only difference is some methods that detect if a number is negative will return true instead of false, but otherwise, JS treats -0 the same way as 0
4
Oddly enough, out of all of these the one the compiler has the best chance of optimizing out is the last one
deleted by creator
What?
First one is optimized obvious.
Second one optimizes to x = 10 via constant propagation.
Third one first unrolls the loop, propagates constants including booleans, and then eliminates dead code to arrive at x = 10.
The last one cannot be optimized as “new” created objects that get used, nextInt() changes the state of those objects, and the global state of the random number system is impacted.
Not if Random writes to global state, that’s a side effect that must be preserved
That’s not even enough to get you a job these days.
You now have to use:do { x = reinterpret_cast<int>(AI::Instance().ask("Do Something. Anything. Be efficient and productive. Use 10 tokens.")); } while (x != 10);You’re absolutely right! Who sets a variable these days without running it though a LLM?
It would get you promoted at Twitter, where lines of code is the productivity metric.
If only I could measure the quality of my paper purely by word count…
I thought “a a a a a a” x100000 was thought-provoking and well tested.
it takes two instructions to materialize a constant in risc-v. X64 has LEA.
Risc-v is better!
I once was helping to organize the testing of town-level algorithmic competition for school students.
The competition had one entry level issue that was basically solvable by reading the question properly, recognising that it’s just multiplication of two numbers, and writing the simplest app ever.
And there was one student who passed the automatic tests. We had to read the code too for the protocol, just to make sure there was no cheating.
We looked in the code. What? Why? It had two nested for loops and a++ inside. When we understood what’s going on we couldn’t stop laughing for like solid ten minutes.
Multiplication is just repeated addition :) glad it worked for the kid, despite the… inefficiency.
Probably Microsoft: You’re hired! Go work on GitHub
I’d say Meta hiring someone to work on WhatsApp. Man, is that piece of software crap… Every update, a new UI bug/glitch appears
The compiler will optimize it anyway. /s
Not sure about the last one though. The other two are trivial to optimize away.
An infinite loop canot be ruled out in the last case, so a compiler couldn’t optimize this away without potentially changing the program behavior.
Infinite loops are often weird though. They could be seen as undefined behavior and the compiler may do whatever it feels like.
How could an infinite loop be considered UB?
Even though this isn’t C, but if we take from the C11 draft §6.8.5 point 6 (https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf):
An iteration statement whose controlling expression is not a constant expression, that performs no input/output operations, does not access volatile objects, and performs no synchronization or atomic operations in its body, controlling expression, or (in the case of a for statement) its expression-3, may be assumed by the implementation to terminate
“new Random().nextInt()” might perform I/O though so it could still be defined behavior. Or the compiler does not assume this assumption.
But an aggressive compiler could realize the loop would not terminate if x does not become 10 so x must be 10 because the loop can be assumed to terminate.
You jest, but you aren’t wrong. At least if we are talking about C, C++ or Rust. https://godbolt.org/z/oPPfdfcf5
.NET compiler is weak when it comes to optimizing your code; I assume Go’s is as bad.
Technically yes… But I think he was more making the excuse for the gore “from the goresmith’s perspective.”
And I’m not sure if the compiler in any language would change a random check function… The others are a possibility.
function myFunction() { try { x = new Random().nextInt(); if (x != 10) { throw "not 10"; } else { return (10) } catch(err) { myFunction() } } } x = myFunction()Commit notes: Added error handling
Returning 10 instead of x when x finally ends up being 10 really ties it together.
I’m glad you noticed. That was my favorite part too.
SyntaxError: Unexpected token ‘catch’
Coding on mobile is hard
For a time on Reddit (some years ago when I still used it) there was a trend of finding the worst way of implementing
is_even(x: int) -> bool. My contribution to that was a function that ranAckerman(x,x)flipping a Boolean at every iteration, and check if it was true or false at the end.It works btw, I will find the proof later
I would love to see the implementaion.
The implementation is not very exciting, I capture a variable in python. It could have been done more cleanly.
The proof is this. But, I could have made mistakes, it was many years ago.
Note that in python you’ll never be able to run
is_even(5)the stack cannot handle itEdit: daaaamn, that variable is ugly as hell. I would never do things like that now.
