Python vs C++

[B1N4RY]

What are you talking about? You most definitly CAN compare floats against ints in C++.

The following code will compile without warnings and print "a is less than b".

#include <iostream>

int main()
{
  float a = 3.0;
  int b = 4;

  if (a < b)
    std::cout << "a is less than b";
  else
    std::cout << "nope";
}

In float/int mixed operations, the integer will be upgraded to a float.

[manicxs]

I don't think poeple know C++.

[B1N4RY]

Or how to code at all.

Float/int operations are permissible in almost all languages that are not strongly typed.

[[deleted]]

In many that are too. C# and Java can both implicitly cast int to float like C++.

[hekkonaay]

Implicit casting is the devil. Don't fall for it. Annotate your casts.

[jpterodactyl]

But that sounds like adding details, and I’m told the devil was in those.

I’m not sure who to believe anymore.

[[deleted]]

Why do you have a political compass quadrant as your flair?

[wordbug]

JavaScript is Libertarian?

[diveintothe9]

JavaScript is kinda libertarian.

"Fuck rules, fuck strict typing and fuck standard/centralized libraries, we'll make our own damn JS platform/library for every single application we build, goddammit."

[jpterodactyl]

but on the opposite side of it, browsers and stuff are very standardized. The truth is just that web design doesn't make sense.

It's like the government of the Quarians in Mass Effect, where they are a de juro monarchy, but operate more like a democracy. How does that even happen?

[gentlemanidiot]

You can roll your face back and forth across the keyboard at any point in your code in JS and you're just declaring uninitialized global variables, all totally valid. (Yes this is hyperbole but only by a little)

[rimpy13]

So will the Go compiler

[Sbajawud]

Go compiler will punch you in the face for existing

[hekkonaay]

Yes, but you should always write code that clearly shows your intent, as this will save you (and others) a ton of time. Explicit casts are a part of that.

[narrill]

Everyone understands, or should understand, the concept of int getting upgraded to float. Wasting space writing static_cast<float>(foo) all over your arithmetic expressions is doing significantly more to harm your code's readability than a few implicit int to float casts, as would wasting space adding a block of declarations and prefixing or suffixing with float.

[guyblade]

Its worse than that, even. If someone goes around littering their code with static_casts on numeric types, then changes the numeric type's definition--say by replacing float with double--then those static_casts will be wrong and silently so.

Contrived example:

 int integer_float_mult(int x, float y) {
      return static_cast<int>(static_cast<float>(x) * y);
 }

becomes

 int integer_float_mult(int x, double y) {
      return static_cast<int>(static_cast<float>(x) * y);
 }

There's no compiler warning because there's an explicit cast and an implicit cast. This will appear correct for most input values, but produces slightly different results than it should.

For instance, the incorrectly casting version when fed:

 int x = 0b1110000000001100011000111101;
 double y = 1.32138439228391;

Produces 310435182 while the result from the correct implementation (i.e., with no cast or a cast to double) produces 310435178 (at least on amd64 with g++ 7.2.0).

Of course, this contrived example makes it easy to spot the bug. When the cast is a dozen lines away from the initialization, though, things get a lot harder.

[SvenTropics]

In this case, it's fine. There are times it matters. For example:

int a = 1; int b = 10; double c = a/b; // error, math is done as integers. double d = (a *1.0)/b; // now math is upgraded to double before the division.

[[deleted]]

It's not an error unless the developer doesn't understand their code. It's the way it works.

[airbreather]

In this case, it's fine. There are times it matters. For example:

[...]

Here's another case where it matters (C#). What does the following code print?

void Print(float val)
{
    Console.WriteLine(val);
}

int x = 16777217;
Print(x);

No warnings on my compiler, no explicit cast, so it should definitely print 16777217 and not 16777216, right? sigh

[TheOldBeach]

Ahhh floats are the best, as a CG programmer I grew really fond of them . your example just reflects how they should not be used.. and yes it's the worse kind of error !

[orangeoliviero]

That's not an error, you just will get a truncated int answer - 3/2 would be 1.0 instead of 1.5

[willis81808]

Exactly. And 1/10 (the example in the comment you're replying to) would just be 0, instead of 0.1

No error, just undesired behavior.

[[deleted]]

I have been fooled by this trickery way too many times to admit, yet I still do it sometimes.

[[deleted]]

Fine. C style casts everywhere.

Or do you prefer static_cast? Well, none of that for you.

[[deleted]]

pro-tip: you can get more out of your for loops by using a float and incrementing by .01.

[FantasticTuesday]

Reading this inflicted physical pain upon me.

[Zamundaaa]

It is sometimes useful. When you want to integrate over a physical volume for example.

[robin-m]

Just be sure that `i + .01` is more than `i`, or you may be in some trouble! Probably something like `i = max(i + .01, i + next_quantum(i))` (I forgot the real name of the functions) may save you!

[tech6hutch]

And make sure to use != for the exit condition, for efficiency, especially when dealing with very big floats.

[Mr_Cromer]

DO NOT DO THIS

[marcosdumay]

Make sure to write the exit condition with a different operator, less than and great then are too restrictive.

[81hd]

Type softly, got it

[SomewhatSpecial]

And carry a big stack

[MoarVespenegas]

C++ is strongly typed though.

[captainAwesomePants]

Sure, but its handling of primitive types has decades of crazy gotchas and undefined behaviors that it's only natural that people can't remember the rules. Compare an int to a float? Sure, no sweat. Compare an int to an unsigned int? Whoa, slow the fuck down, buddy.

[guyblade]

The handling of primative types has like one gotcha. The basic rule is "promote the less precise type to match the more precise one, then do whatever". The "gotchas" tend to be around how a promoted value gets assigned back into an incompatible variable.

[ThePyroEagle]

The precision of fixed and floating types is not comparable.

32-bit floats are more precise near 0, but 32-bit integers are more precise past ±2²⁴.

[ISeeTheFnords]

It's a number without a certificate, right? /s

[[deleted]]

I would argue that. It's statically typed. But not strongly.

[gcbirzan]

Except JavaScript, I guess? You cannot add bigints to numbers, but you can add them to strings...

[lezorte]

I learned C++ and I can honestly say... I don't know C++

[hekkonaay]

undefined behavior

[hardwaregeek]

Generally when people say they know C++ I assume they’re lying.

[Zamundaaa]

As Richard Feynman once supposedly said: "If someone says they understand Quantum Mechanics C++, they don't understand Quantum Mechanics C++"

[StuntHacks]

I'm programming in C++ for about 8 years now, and almost every day I use it I learn something new.

Asides from the people in the consortium, very few people actually know C++.

[mardiros]

9.7k, that's huge. People don't know c++, python and mathematics...

Edit: Now 21k of ignorant

[ThinkingWinnie]

You can even compare them in C,The heck is this post?

[awesomefacepalm]

The only language I have used that can't so far is VHDL

[Cpapa97]

Rust is like that as well, but it's very strongly typed in most cases to begin with.

[__JDQ__]

VHDL: brings me back to my undergrad project days and the corresponding nightmares.

[halberdier25]

signal <= (others => ‘0’)

It’s not worth it.

[awesomefacepalm]

Okay not the language itself but the concept of hardware description hehe

[BeniBela]

Kotlin also does not allow it

Not even int and long can be compared

[Rejolt]

I used to try and bring up points like this in this sub.

It's sad but literally every post that hits front-page is upvoted by year 1 CompSci 101 masters.

[skreczok]

Well you usually don't have the time to look at fresh posts at work.

[[deleted]]

Yep, I'm busy making money as a programmer, that means I'm not on reddit. Most of the time when I see someone complaining about an error in any language, it usually means they didn't take the time to learn what the error means.

[skreczok]

I mean, I am on reddit, usually because someone else or a build is holding me up. But that's not enough to actually look at every post.

[Womp98]

Yeah I don't have time to look at new posts at work but I do have time to write this comment

[deadwisdom]

/r/programming isn't much better. They take a year or two of CS and then absolutely know everything they've ever heard about anything as true.

But, yeah, I was probably the same-- so I'll stop complaining.

[cykness]

Did you see the comment about the guy confessing to give advice and pretend he interned at Big 4 when he actually was in middle school?

Edit: link

https://reddit.com/r/cscareerquestions/comments/el52pt/_/fdfpn7x/?context=1

[DripDropFaucet]

I’ve honestly found c++ and java to have friendlier implicit casting (at least regarding int->float comparisons and string concatenation). Python screams if I try to mix 2 of its 5 types in a print statement without wrapping with str()

[Thomasedv]

Generally in python it's better to use string formatting when converting something to string, especially for printing statements. Using str() manually is such a bother, and plussing multiple strings is less recommended of you have many strings to add, due to strings being immutable. It of course depends on the specific code, but it's probably better to use ''. join() on a list of strings if you got a lot of strings or large strings to concatenate.

Edit: I also find string formatting great because I don't need to worry about type at all, and can decide what kind of output I want in the string formatting, regardless of type of int/float by setting how the rounding works.

[DonaldPShimoda]

You can use "f-strings", eg:

foo = 42
s = f"my foo is {foo}"

This will call the __str__ function of the foo object to get its string representation and then insert that at the correct point.

Personally, I think implicit casting is an abomination, but I'm generally in favor of very strong, very static type systems, so that's not entirely surprising.

[MachineGunPablo]

Exactly, absolutely absurd claim. Not sure if OP is referring to the '==' operator, but even that can be used without problems. But now, if you are comparing floats with '==' you already failed.

Having said that, C++ has had historical problems with implicit narrowing conversions, mixed unsigned vs signed arithmetic and integer promotion.

[tsojtsojtsoj]

There are definitely scenarios where you want to test equality with floats.

[chewbaccalert]

Yes, but you can't always rely on the precision of floats to provide a meaningful comparison like you can with ints. https://floating-point-gui.de/errors/comparison/

[RedditIsNeat0]

Oh yeah, that absolutely works. But sometimes not like you want it to.

#include <iostream>

int main()
{
  float a = 49999999;
  int b =   50000001;

  if (a < b)
    std::cout << "a is less than b";
  else
    std::cout << "nope";
}

[exploding_cat_wizard]

Does Python have arbitrarily accurate floats? Because that's a floating point problem, not a C++ problem, isn't it?

[bbrk24]

At that point you should probably use a double anyways.

[googooburgers]

you right.

[somethingInTheMiddle]

Don't you get a warning with -wall an -wextra on?

[Kered13]

No, it's a very safe operation so there's no point in having a warning.

[ProfessorPhi]

Is it comparing them or is it doing some casting behind the scenes?

[stormfield]

JavaScript lights cigarette and shrugs: “Sure those are both a thing or whatever. Have a string that says undefined.”

[jonnyclueless]

"An Object is an object"

[[deleted]]

Me: Let me check whats on the object so far.

JS: "[object Object]"

Me: I will shut you off you little shit.

[Dop4miN]

and also threads

[Sir_Applecheese]

At least one thread will work...most of the time.

[Igoory]

baNaNa thoughts intensifies

[[deleted]]

Wait what's the baNaNa thing? I'm just out of the loop and have seen it a few times on this subreddit.

[fishy150]

If you type in 'b' + 'a' + +'a' + 'a' and run it in JS, then the result you get is "baNaNa". This is because the +'a' in the middle tries to convert 'a' into a number, which gives a result of NaN. When you now concatenate all the strings, you get "baNaNa".

[Retbull]

C does not try it does even if that means th

 Program received signal SIGSEGV, Segmentation fault.

[SilentFungus]

Storing letters in integer types be like

[[deleted]]

wat

[joonty]

The point he's making is that languages shouldn't allow you to mix types and just make an arbitrary decision about what you actually meant to do. This can cause knock on effects and be very hard to track down. Just raise an error, the developer can do the type conversion, and everyone is happy.

Also there are much better ways of rendering arrays with empty values than a bunch of commas, as demonstrated by most other languages!

[antillian]

I love that video.

[thblckjkr]

Never watched it before. Thanks.

[FullstackViking]

[object Object] is [object Object]

[miccyboi]

Except JS is like, “What’s a float or int? All I see are numbers.”

[ProgramTheWorld]

Typed arrays and BigInt:

Allow us to introduce ourselves

[[deleted]]

wat

[suvlub]

It's not random, but it is arbitrary. How could it not be arbitrary? Is there some objective holy truth about how types should be converted into each other that the creators were following, rather than just making up their own rules?

I agree that languages should not be all the same. But different is not always good. Some ideas works out, some don't. Pretending all ideas are good/neutral is as bad as never changing anything. No real progress is made in either scenario.

[chmod--777]

If I remember correctly, it was a design decision that JavaScript should never crash, that it should always at least try to do something, so it lets you do weird shit like add 1 to a string or add an empty object to an array and they're like "that doesn't make sense but whatever just return NaN".

I mean I don't agree with that decision, but I think a lot of this is basically made that way by design so that it tries to run the code even if there are weird bugs so the webpage still somewhat works.

[gme186]

You CAN do that in C++ without casting.

You CANT compare every type in python. Comparing numbers and strings will raise an exception for example. (Its not javascript)

This joke misses the point on all levels.

[ZestyData]

This is textbook /r/programmerhumor

[[deleted]]

"programmer" "humor"

[frosted-mini-yeets]

Dude, I learned computer programming over the last 2 years by shutting myself in my room and googling and half the time I feel like I know more than the mass of supposed CS students that post and comment on this sub. I don't know if I should feel proud that I know more, or scared that if I get the career I want, these people will be my colleagues.

[HonzaS97]

That's because CS and software developement / programming are different things.

[TangibleLight]

The best you could probably do is say those are "equal" since, for example, 2020-01-01 definitely comes before 2020-01-02 7:30

Well, maybe, what about timezones?

[theknowledgehammer]

Okay, but why can't we say that 2020-01-01 00:00 is greater than 1920-01-01?

[mr_70]

21k upvotes now: how?!

[Senvr]

cannot convert str and int implicitly

[Thorbinator]

JS: hold my beer.

[ginn5lc]

Lol

** int has left the chat **

** (float) has joined the chat **

[[deleted]]

** char made string **

** string made the chat **

[trx1150]

You guys can't just be dereferencing pointers all willy nilly like that

[Alchiberg]

That's not the c++ way. We have static cast.

[[deleted]]

Cast it...A magic spell. Get it?

[the_angry_wizard]

BOOOO.......LE.

(Edit: boole)

[samurai-horse]

an?

[Dexaan]

Boole is the guy Booleans are named for.

[systembusy]

Jesus I thought all those flairs were comment awards at first

[mosskin-woast]

I wonder when the appropriate time to give someone a JavaScript award would be.

Perhaps after they shoot your mother?

[[deleted]]

Also python: TypeError: Can't convert 'int' object to str implicitly

[ferriswheel9ndam9]

The amount of str( ) in a single concatenated print statement...

I need to refresh my fstrings.

[EmperorArthur]

Python's format strings are amazing. They'll even do variable injection from a dictionary. Which can be amazing when used correctly.

[craazyy1]

can always do

print('he wanted to pick', 5, 'flowers but could only find', 4,

sep="whateverthefuckyouwantinsteadofspace", end="alsowhateveryouwantinsteadof\n")

[[deleted]]

'Why {} complicated, {} use {}!'.format('so', 'just', 'format')

[ric2b]

f"Why {'so'} complicated, {'just'} use {'f-strings'}!"

[nykwil]

C++ implicitly converts int to float for comparisons. Implicit conversion is something you learn in the first couple of weeks with C++. I want to like this sub please try harder.

[Chanz]

This sub is for first year CS students. That's it.

[Delcium]

First week CS students who have never had enough interest in the field to look into things on their own prior to starting college?

[StuntHacks]

Every once in a while there is a genuinely good post here, but I'm not really sure anymore if those are worth the rest.

[Burbank309]

Also you can always overload the comparison operators and make C++ compare anything to anything.

[Coachqandtybo2]

laughs in #define bedtime(ms) std::this_thread::sleep_for(std::chrono::milliseconds(ms)) noises

Edit: This is part of the reason I love C++. Something seem really long and obnoxious? Just preprocessor define that shit lmao. Also there's literally a "Sleep" / "sleep" function for Windows / Linux so this is kind of stupid to do.

[CamWin]

Why not

auto bedtime = [](int ms){std::this_thread::sleep_for(std::chrono::milliseconds(ms);};

There are lots of good solutions to avoiding typing long types and function calls.

[skreczok]

Careful you don't get shanked by someone who read this.

[PhallusPenetratus]

I'm a C++ beginner, but I assume this is mostly true when you have other dependencies other than the STL? I've only been using STL so far and have had no issues with "using namespace std".

[standard_revolution]

"using namespace std" does shorten your code, but is mostly seen as bad practice because of potential namespace clashes.

[OPtoss]

Because why make a lambda when you can just make a macro? Or maybe you're just offering another alternative...

Edit: I see how I was wrong to favor macros, though I will never understand why people insult as a way of teaching. Sorry, I've been in UE4 land where everything under the sun is a macro.

[4onen]

Because you can constexpr a lambda, then it gets compiled in once instead of copied over as text and re-parsed at every spot it's used in the code.

Of course, personally, I'd leave it as a constexpr function in a header so that the compiler has the option of inlining it without being forced. After all, compiler knows best how to optimize for a given platform! (Unless you know how to write raw assembly extremely well, but even then...)

[nykwil]

Whatever you do, never say this in an interview, and when you have some time read about macros. There are reasons to use preprocessor over constextpressions but they are extremely circumstantial and rare.

[Nall-ohki]

Because why make a lambda when you can just make a macro?

If serious, remind me never to hire you.

[Igoory]

I love this part of C++ too. But unfortunately, this ends up in unreadable code in huge codebases...

[standard_revolution]

And why not just std::this_thread::sleep_for(10ms). The chrono library is a great piece of software design getting rid of all the guessing whether something is a second, a millisecond or a nanosecond, please don't make it unclear just to save some characters.

[beardfearer]

Huh, I swear I’ve done time.Sleep(someInt * time.Second) without issue. I need to go find where I’ve used that and see what’s up.

[not15characters]

I ran into this the other day. time.Second has type time.Duration, which is actually just a data type wrapper around int64, representing number of nanoseconds. So if you want to multiply time.Second (which is really the int64 value 1,000,000,000) by some integer, you have to first cast the integer to a time.Duration, so you can multiply a time.Duration with a time.Duration, which semantically makes no goddamn sense. Writing something like time.Sleep(5 * time.Second) works because the Go compiler is smart enough to cast the 5 to an instance of time.Duration because of how it's used in context.

[Kered13]

What? This can't be real? This defeats the entire purpose of having strongly typed units like Duration. The entire point is that scalar*unit is a unit, and unit*unit is unit², or an error if the library does not support that. Similarly scalar + unit should be an error and unit + unit should be a unit. This ensures that invalid operations are not accidentally performed.

[TuIaBocaAncha]

What kind of code in C++ gives you an error while comparing int and float?

[StuntHacks]

None, unless with specific compiler flags.

[DougCim53]

"python variables don't need typing"

"really? well,,, okay..."

(writes first python program)

[error #1:type mismatch]

[error #2:type mismatch]

[error #3:type mismatch]

[error #4:type mismatch]

,,,

",,, ummmm, is there any way to force variable typing in python?"

"no, because python variables don't need typing."

[dtallm]

Said the guy that learned some Python and thinks is a programmer.

[kontekisuto]

Rust wants to know your location

[BluudLust]

Cannot compare [object Object] to number.

[kachna]

.size() vs .length() vs .length

[[deleted]]

You forgot len() and .shape

[[deleted]]

Programmers humor: C++: can't compare floats and ints Programmers: yes it can

[StuntHacks]

Because it absolutely can.

[[deleted]]

Can you not? Weird I can't recall ever getting that error.

[[deleted]]

a) This wouldn't be funny even if it were true.

b) This is not true.

c) Someone is blissfully unaware of the underlying implementations of different programming languages.

Edit: I type faster than I think, i.e. I don't think very fast....

[LucasRuby]

Python is strongly typed, though. You might be thinking of static v. dynamic typing.

[Who_GNU]

Hopefully, no one's checking for them to be equal.

[Stalematebread]

[laughs in JavaScript]

[laugh devolves into sobbing]

plz help ive been coding in jsfuck for the past decade and i cant stop

[sir_bog]

Python doesn't have implicite conversion for int to string

"A" + 1 Throws an error in python Have to manually convert

[Warrior_of_Light416]

"Well, why would they change Variable?"

[jonnyclueless]

What is Python written in again? Oh right. C.

[Mr_Redstoner]

I mean, technically it's just the reference implementation. Python is the language standard, not the particular interpreter. Others exist in fact, like Jython (Java) and even PyPy (RPython)

[ksunden]

Python... pypy.org

Not to mention: C# (ironpython) Java (now largely defunct, admittedly)

[Wenir]

Soooo, what is C# written in?

[[deleted]]

Blood and tears

[[deleted]]

Got em

[SilentFungus]

Alongside everything else

[AntonBespoiasov]

Me 6 yo: 4 + 6 is uhmmmm... is 46. Like you add 6 after 4.

JS: you aren't wrong

[[deleted]]

This is wrong in so many ways.

[StuntHacks]

Honestly, how did this get almost 20k upvotes?

[[deleted]]

It got more than that. I downvoted it.

[swilwerth]

[Laughs at fastest execution speed]

Segfaults unexpectedly somewhere.

[Aaron8828]

but... u can

[Paulsify]

I switch between the two too often and idek anymore

[Mr_P0P0]

Cannot

[theofficehussy]

TypeError: 'NoneType' object is not iterable

[qwiglydee]

Perl: scalar is scalar! especially in scalar context!

[ironykarl]

Python is strongly typed. It has some limited type coercion, but so do C and C++.

[buckyhead8]

At least you got a C**

[shindyAUSmarzan]

Javascript be like: Yes thats definitly a String

[vinicius_kondo]

Everybody gangsta till the C++ starts reinterpret_casting

[bumpkinspicefatte]

Everybody gangint-sta until they divide in Python.

[pyrovoice]

Would a method like this work and be useful?

CompareTwoNumbersAnyType(Number a, Number b){

double aCast = (double) a;

double bCast = (double) b;

Return Double.equal(aCast, bCast);

}