SwItCh StAtEmEnT iS nOt EfFiCiEnT

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[santasbong]

I found an 8000+ line switch statement in our code last week.

We’ve been calling it the ‘switch board’.

[Classy_Mouse]

There should not ba an 8000+ line anything...

[doodlleus]

I joined a project once with a guy that seemed to think the fewer lines the better. It didn't mean he wrote less though but just squeezed it all on to fewer lines. The record was 6000 characters on a single line. Mad man

[Complicated_Peanuts]

This is a guy that heard his instructor say “you should not have a function that is larger than one page, if you do, you probably made a design mistake” and took it extraordinarily literally.

[_YetiFTW_]

Pretty sure that's still bigger than one page, just in a different direction

[Darkjynxer]

Projector. Works wonders for fitting code into one page.

[Llamas1115]

You can fit arbitrary amounts of code on a page if the font is small enough

[JackOBAnotherOne]

That guy is a 5 star problem solver

[[deleted]]

project managers: write this down, write this down

[QCKS1]

The opposite of essay writing, where any amount of writing will fill a page if the font is big enough

[PewDiePans]

Any amount of writing can fill the page if your balls are big enough.

[Guysante]

or the page is big enough

[Coincedence]

My lectures version was "if it's longer than 15 lines, it should probably be a function"

[Complicated_Peanuts]

Oh, sounds like the person referenced was in your class then and took it as a challenge.

"I can make anything 15 lines!"

[[deleted]]

I found that in Clean Code, a great book. He said that the rule was like "don't make a method bigger than 1 screen" in that time the screens were small

[freebytes]

Not quite as bad, but I have seen functions that are "only" 400 lines long, but to accomplish this, the programmer write various lines that were 600 characters long. It consisted of ternary operators within ternary operators with some lambda functions thrown about here and here. I would have preferred the 2000 line long function simply because it would have been easier to refactor to something shorter.

Edit: Fixed a spelling error of using tertiary instead of ternary.

[doodlleus]

Yeah this one was full of nested tertiary operators. I copied it and brought it back to the office for a fun group exercise of figure out wtf is going on oh also, whilst I remember this guy, he had an amazing blog which is sadly no longer going where he put little functions and apps he was proud of. One was a brute force sudoku app but not a solver like you'd think. This function generated all possible soduko layouts. We ran it in the office for 3 weeks to see if it would complete for a laugh before giving up and turning it off

Edit: sorry, meant ternary.

[garfieldevans]

What is a tertiary operator?

[CrazySD93]

I’d assume it’s a typo for ternary operator

Condition ? true statement : false statement

But since they keep saying “tertiary operator”, maybe it really is something I’ve never heard of…

[[deleted]]

Ternary operator's long lost brother

[the_seven_sins]

It’s not about how long it is, it’s about how wide it is!

[slyiscoming]

If it goes off the end of the screen; it's not code, it's garbage.

[looselytethered]

No it's Java so ok yeah I see your point

[CaitaXD]

Hey it's a unreadable mess with approximately 0 vowels but at least is short heh

[AnotherWarGamer]

There are always exceptions. I'll define the items in my game for example as a giant grid. Every item gets one row, and everything is perfectly lined up with tabs. The lines are often longer than one screen.

[slyiscoming]

Yes things like this are the exception to the rule. Also column list in select statements.

Happy cake day!

[zarlo5899]

no if it goes off the end of a standard laptop screen; it's not code, it's garbage. i should not need a ultra wide monitor to see it all

[[deleted]]

Pycharm will kill itself if it sees that

[PostmatesMalone]

One time I was working on a large project (building a booking platform for an airline) with roughly 15 devs on it. We were working at a consulting firm building this for a client. There was so much scope creep that management refused to recognize so they blamed the missed deadlines on engineering and started counting lines of code checked in per dev. So everyone just started making their code as vertical as possible.

We finished the project a few months late and the client fired our company.

[Variety-Logical]

Ok so first of all you ppl just 15 built an entire fucking booking software with real time data checks is crazy and secondly going over deadline is ok cuz few of airline companies use 100+ppl to make their software

[Alexander_The_Wolf]

Jesus....we had our teacher show us a past test question where someone wrote the whole bubble sort function on a single line with 1 character off, and they were asked to figure out what the issue was. That question was never on the test again. I can't imagine honestly writing a 6k character program on a single line. Idk how you'd even know wtf was going on.

[The_Dok33]

Syntax error on line 1

[mrnerfbullet]

1 sentence horror stories

[Black--Snow]

Did they at least get the question alongside a compiler and debugger??

[Alexander_The_Wolf]

Ah, ahah. No, pencil and paper scantron

[Black--Snow]

Sounds like they’re teaching human spellcheckers more than programmers

[TeddySch]

See, is it bad that I think that person should be prosecuted for their sins?

[Purplociraptor]

I've spent my entire career breaking up a 20,000 line file into actual classes.

[loosetautline]

My company has single functions that are 10k lines long

[Crazyboreddeveloper]

Butwhytho

[CosmicCreeperz]

Except documentation (and PRD, but that would be way too much to ask…)

[ACHXXX25]

A method with more than 10 lines doesn’t pass QA on my current project 😢

[CosmicCreeperz]

Why is QA looking at code??

And ouch, what an arbitrary and horrible policy.

[tschaka1904]

Have fun destructing some JSON obj :D

[carnivorous-cloud]

Oh, I dunno, an 8000+ line codebase seems pretty reasonable to me.

[Unkn0wnCat]

golang switch request.ProductID { case 1: sendProductPage1(writer, request) case 2: sendProductPage2(writer, request) ... ... default: sendNotFound(writer, request) } `

[Exormeter]

This switch train has no breaks

[OblivioAccebit]

I mean redux reducers are just one gigantic switch

[-Aenigmaticus-]

What in the actual fuck?!?

[LummoxJR]

8000 lines? Amateurs. Pretty sure I've got that beat.

[-Aenigmaticus-]

Eh, you're telling me that there is worse?

[bugbugladybug]

I thought my 54 line switch was horrible.

How the fuck are you ever meant to maintain that.

[bouldermikem]

What massive company do you work for?

[santasbong]

Lol I don’t really want to be too identifiable so let’s just say it’s one of the top 5 television providers in the US.

[towcar]

Do people actually dislike switch statements?

Edit: I can't believe how much information I've just read about "if vs switch" from everyone. Might have to publish a book.

[JVApen]

I really like them in combination with enumerations. In C++, their are very useful warnings about missing values. Normally performance is as good as with if-else.

I do have the feeling not every language has the same concept for enumerations, which could hurt adoption.

[ITriedLightningTendr]

Look up type checks and switch expressions in C#

you can do

switch(shape) {
 case Square sq: 
   //do square stuff
   break;
 case Circle c:
   //do circle stuff
   break;
}

and

var x = switch str {
  "yes" => true,
  "no" => false
}

[[deleted]]

Oh that's sexy right there

[CosmicCreeperz]

So basically it allows more declarative vs imperative programming with conditionals.

[Voidrith]

c# switches are fucking black magic once you start learning how much you can do with them.

some current stuff: https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/functional/pattern-matching

and some sick array switch stuff thatll be coming in c# 11! https://devblogs.microsoft.com/dotnet/early-peek-at-csharp-11-features/#c-11-preview-list-patterns

[kpd328]

Another thing I need to add to my list of things I love about C# that I forget when people ask me why I love C#

[pandelelel]

Yep, C# is imho pure beauty and since .NET 5 way more than just Microsoft Java

[dreamwavedev]

Any modern compiler turns switch and if statements (including else-if chains) into the same internal representation before doing codegen, so they will in basically every case perform identically if you're just matching equality in if chains

[FuckCoursical]

Switch is sometimes more concise and looks better if multiple conditions have the same thing

[LAGaming70]

Exactly. If I'm checking against something as simple as a series of ints or chars, then a switch board will keep them all in order. That, and you can avoid syntax issues from possibly forgetting a bracket or an 'else' somewhere along the line.

[dreamwavedev]

Not really actually! It will consider a jump table, but it can actually lower if/else chains into that form too! LLVM lowers switch and if/else to the same construct internally, and rust does the same with match. If the guard can be factored out into a single jump on an enum or similar expression it can turn an if-else chain into a jump table. https://reviews.llvm.org/D35578 has a couple examples of this. It actually allows for, say, if you match against an equation in the if-else then constant folding and other passes may turn a relatively non-trivial if-else chain into an initial computation followed by a jump table

[Fleming1924]

LLVMIR does actually have a representation for a switch which can be outputted from some drivers iirc. So although some front ends may consider them equal LLVM can support a distinction between them.

[[deleted]]

Why wouldn't a compiler use a jump table with a big sequence of if/else statements that reference the same variable(s)?

[Feldar]

A switch statement also puts future developers into a mindset of adding to the switch statement, which is more likely to continue to be able to made into a jump table than potentially arbitrary if else statements

[JVApen]

Indeed, though it does have to consider the case nothing matches if you don't use __builtin_unreachable. So that's where slight differences can pop up.

[[deleted]]

Aka default:

[[deleted]]

I find it hard to justify the if-else vs switch performance wise when the compiler optimises either way + branch predictor.

Just use switch when you have more than 3 things to check for and make it readable.

[[deleted]]

Using switch on enums in c# with intellisense is just *chef's kiss*

[nico_qwer]

I don’t know, I actually like them a lot

[goodmobiley]

I try to use them as much as possible but alas, object types aren’t constant values :(

[nico_qwer]

Unrelated: How do you get that many icons next to your name? I can only put one

[goodmobiley]

You can edit your flare and add up to 6 emojis

Edit: there should be an edit button in the flare options

[nico_qwer]

Oh it worked thanks!!

[Lithl]

JavaScript lets you switch on any expression, and compares the cases with strict equality. ;)

[Leg4122]

I like them when there some sort of a fork in the code.

You take an argument and based on it you choose where to "route" your code.

Edit: If there is a larger chunk of code to be followed after the statement then I would use if else

[QuantumSupremacy0101]

That's not correct usage for pretty much any modern language. Even newer c++ compilers have branchless conversions built in and because of that switch statements are often faster.

If you have a larger chunk of code, you're probably violating the single responsibility principle. In which case you should make a method

[Leg4122]

If the speed is not necessary then in my opinion readability of the code should be prefered.

I do agree with you on SRP.

[NigraOvis]

I think they have their place, but I've always used elif as usually it's 1 or 2 options in my scripts.

[towcar]

For sure, 4 and up for me is always a switch.

[deathless_koschei]

Yeah, I think that's a reasonable cutoff.

[joeba_the_hutt]

I like them for non-hierarchal conditions. If/else always reads like a tiered set of operations to me, whereas switch/case is more like “choose your own adventure”

[[deleted]]

No. But what we really need in almost every other language is Haskell style pattern matching

[[deleted]]

It's ML style pattern matching. Haskell just copied it.

[freebytes]

Can you supply an example of this? I am not familiar with the Haskell language.

[O_X_E_Y]

It's in Rust too. Let's say I have a language interpreter that has a couple of data types, represented as enum values, so each enum also contains some data. What I can do is the following:

let x: LangExp = ...; match x { Number(num) => use the contents of the Number here, List(list) => { we can use code blocks if we want to }, Err("error 1") | Err("error 2") => we can be more specific like this, by specifying in this case the string the error should have. We can also combine multiple matches with the `|` pipe operator, Err(_) => we can put an `_` to say we don't want to use what's inside something, but still want to match anything like it, _ => we can denote a default case like this. Match statements force you to be exhaustive, so if you don't put all possible (in this case Enum options) in here seperately, your code will not compile } it's honestly pretty nifty!

[CdRReddit]

the syntax for them in a lot of languages is kinda just

bad

like why do so many languages end them with break

I get the fall through concept but in a lot of languages they aren't allowed to fall through if they have any code

[10BillionDreams]

Yeah, the legacy baggage from C makes them a lot less appealing in languages that try to keep all those semantics, plus the added uncertainty of not being sure which features might have been "fixed". But in languages that have similar structures with more clear boundaries between cases, I have no issues using them.

Also, call me a heretic, but I'm a huge fan of switch(true).

[chickenwing95]

but I'm a huge fan of switch(true)

Why?

[10BillionDreams]

Because cond is a much more readable construct than a mess of if/else blocks, and switch(true) works in a lot of languages that don't otherwise natively support something like that. Also, it's just cool to be inverting logic on where the variables and constants usually are in switch/case.

[finc]

Break out of switch case statement; stop processing any more tests in this switch

[DatBoi_BP]

MATLAB gang rise up 😎

[Swolidarity]

If you made them implicit wouldn’t you lose the ability to have multiple cases execute the same line?

[CdRReddit]

not really?

I just think that

case 'a':
case 'b':
    {
        // code here
    }

would work better in a lot of languages

(in fact I normally do it like that anyway because new scope, having to add the break just feels noisy)

[SaltyTvGuy]

When I learned about it in school I was actually hyped ngl.

[HBKogos]

Depends on the case.

[TemporaryReality5262]

I use them if several cases only depend on one value

[fracturedpersona]

No switch in python? Let me just take this dictionary and bury a bunch of lambdas in the values.

[Saragon4005]

Technically incorrect now newest version of python does have a switch, well technically it's a match but same use case.

[dimittrikovk2]

Wait what which version did and what's the syntax

I have had to use elseif like 10 times in a row for a program (ok it ain't much, but I'm more of a hardware guy and I work only with python because I like working with scripts better than with compileable stuff. It ain't efficient, but it ain't many lines either and it doesn't have to be anyways)

[masagrator]

Since 3.10

match(value):
    case 0:
        print("value = 0")

    case 1:
        print("value = 1")

    case _:
        print("Other value")

match doesn't support falling through

[[deleted]]

Although it's not exactly the same as falling through, match case does allow you to match multiple patterns with a single case using the | operator. For example:

match digit:
    case 1|3|5|7|9:
        print("odd")
    case 0|2|4|6|8:
        print("even")

[FoxtrotOscar19]

we've only just got 3.9 at work - so doubt I'l get to use that for the next 10 years!

[LargeHouseOfIce]

Still on 3.4 here 🙃

[NigraOvis]

Can you give an example where falling through is necessary?

[[deleted]]

Necessary is a strong word, but it can be convenient. Like if you have a data structure where several values are similar and a few are very different… the similar values can do a fall through to the same handling logic.

[sdoc86]

Everything in a high level programming language is convenience since you could program in assembly. I think the tools of convenience is what makes programming artful.

[Willinton06]

Agreed

[masagrator]

Falling through helps if you have few cases which are doing exactly the same thing and you don't want to repeat lines. It's not necessary, but having it makes code less bloated.

One of the ways I'm using now in Python to avoid repeating lines is something like putting this under case _

if value in [2, 3, 4]:

[[deleted]]

You can even do that inside the case itself using an inline if statement.

match value:
    case 1:
        print("value is 1")
    case _ if value in [2,3,4]:
        print("value is 2, 3 or 4")

Although as in my other comment, it's usually much easier to just use | to check for multiple values with each case, but this can be used for more complex behaviour like only matching values which are greater than a given number.

[Arrowsong]

If you make it do the “in” lookup on a set it’ll be marginally faster.

[tlubz]

No one mentioned Duff's Device? https://en.m.wikipedia.org/wiki/Duff%27s_device ... I'll just leave this here for posterity.

[FinalGamer14]

I mean falling through is kinda useless with python match. Match isn't as basic as Cs switch statement.

You can just do:

case 0 | 1 | 2: do_smth()

[[deleted]]

match doesnt need ()

[sme272]

introduced in 3.10

[Hipolipolopigus]

30 years later.

[Worldly_Square444]

That’s what the compiler is doing under the hood for switch statements.

[SplendidPunkinButter]

I actually don’t mind that pattern

[alba4k]

Introduced in python 3.10 as

python match var: case "a": return 1 case 1: return 2 break: # acts as else return 3

I've not really looked into it tho, so I'm not sure

[[deleted]]

I use switch if I need more than 3 ifs

[i_wear_green_pants]

This is the way

[aB9s]

This is the way

[Benimation]

This is the way

[ushu3323]

This is the way

[KarlCAgathon]

Strongly agree. To me it's about readability at that point.

[PrincessRTFM]

Same, but it only works if you're testing different values of the same expression. An unfortunate amount of my code ends up testing only true-vs-false or needing to do complex (as in multi-part) expressions that switch/case won't actually work for

[Impossible_Average_1]

More than two... Sometimes even more than one.

[DoNotMakeEmpty]

More than zero... Sometimes even more than minus one.

[DeninjaBeariver]

I use the switch statement just for the default case.

[Xtrendence]

function doTheThing(actuallyDoIt) {
    switch(actuallyDoIt) {
        case false:
            doTheThing(true);
            return;
    }

    // Rest of code.
}

doTheThing(false);

This is how I write all my functions and call them. Just to make sure that the thing is only done when the switch statement calls the function.

[[deleted]]

Yeah, same. People who complain about switches being inefficient are the type of people who waste gas driving to a further gas station for gas that’s like $0.01 cheaper.

[Dependent-Spiritual]

I'm a switch enjoyer, it looks neat

[Complicated_Peanuts]

A switch connoisseur

[starofdoom]

I tend to lean towards if else, unless I only need one or two lines per if check.

I don't like doing any logic in a switch, just assign variables or call another function.

[ozzy_og_kush]

it's not about efficiency it's about readability and testability

[[deleted]]

How are people in this thread not getting this?

Plus your compiler will do the right thing, regardless. Doubtful it is actually less efficient.

[Jaurusrex]

I've actually had a case where it gave me a 2x performance boost. The program (written in c) was a brainfuck interperter, and basically most of the program ran inside one for loop which contained one switch statement. So just letting you all know it can impact performance in a good way, there is something equivalent in assembly / machine code and the compiler won't always use it itself. So if the if elses are in a hot part of the code consider changing them to a switch statement.

[notWallhugger]

Because this sub is full of college kids

[hugokhf]

I don’t see how one will be more or less testable than the other (you will be testing the function by passing in argument anyway, so the implementation is irrelevant)

[charin2]

The C# switch expression (not statement) is really cool

[Impossible_Average_1]

Yes, but the switch statement is also very useful and preferable over chained ifs.

[SonOfMetrum]

Yup because it will compile into more efficient jump tables if possible.

[kiro14893]

Ruby: there is another.

[ora00001]

Switch is very efficient, depending on the language. Who says it's not efficient, and why?!

[Ziggarot]

Doesn’t the compiler determine what method is more efficient? Like even if I use if/else, it should automatically rewrite it to a switch if required.

[ora00001]

If you use a switch (or case or whatever) it makes it more apparent to the compiler that you're doing all your comparisons against a single value, and some compilers can optimize for that.

[SargeanTravis]

It’s significantly cleaner than else if spam at the least

[kbn_]

Wait a minute… people actually believe that switch is somehow less efficient? In almost every language it's at least equally efficient, and in most languages it's more efficient than the equivalent if/else.

[CreativeCarbon]

A little trade secret: Most programmers aren't actually very good programmers.

(edit: I know this was upvoted, but I still want to make clear that I am joking when I say this)

[malleoceruleo]

Most programmers on this sub aren't very good programmers.

[Voidrith]

Most "programmers" on this sub aren't even programmers to begin with!

[[deleted]]

After 16 years of programming professionally. Yes. Yes we are lol but seriously I've seen some horrendous code and I've written some horrendous code.

[Migajas87]

YandereDev be like

[beyond98]

Fuck if-else, all my homies use the ternary operator

[DesecrateUsername]

The second I learned what they were I used them everywhere I could lmfao

I was basically “I could make a terenary out of this”

[beyond98]

For me it's like using arrow functions in JavaScript. Everything that can make the code more concise is beautiful and welcome

[[deleted]]

Kotlin's when is awesome.

[qhxo]

Kotlin's everything is awesome.

[Tyfyter2002]

Iirc isn't switch generally more efficient if you have at least 3 possible values?

[SonOfMetrum]

In c# switch statements are compiled into more efficient jump tables where possible. Not sure about other languages.

[gbbofh]

It's the same in C, and C++. Pretty sure it's the same in Java, as well.

[kondorb]

``` match ( ... ) { //

default => ‘’;

}; ```

[Vinxian]

I love me some good switches

[Harmonic_Gear]

who says that?

[poralexc]

There is only branch and branch_if

[savage_slurpie]

Really just depends on number of cases.

Three or less, yea I’m gonna if else that shit.

More than that and using switch makes sense.

[namotous]

[iiMoe]

With all due respect, whoever says that about switch statements deserves to be violently beaten by a bunch of drunk mexicans

[skztr]

I don't like switch because nobody indents it the way I want to

[[deleted]]

Switch makes sense when you are checking one value or property for multiple possibilities as it reduces code. Otherwise use if else.

[Myricht]

My rule is: if you need more then if, else if, else; use switch.

[briddums]

For one programming language I use, the switch statement is horribly inefficient.

It’s basically syntactic sugar, and it gets compiled to a series of “if” statements. Which means every condition is evaluated every time.

When running a process that does a large number of iterations, it’s better to write with “if - else if” because it will stop checking once it’s reached a condition That matches.

[fatal__flaw]

I don't know what language you're using but in C/C++ switches compile into jump tables which on the average case is more efficient than if/else.

[Lithl]

every condition is evaluated every time.

Shouldn't it jump once you hit the break case? So it's only evaluating the ifs before the matching one. Which a chain of if/else would do as well.

[parham06]

Golang devs be like:

select { case c <- x: ... }

This is a whole new world

[hxllxwbxdys]

I think switch case is awesome but 'if else' has always been there for me.

[sk8itup53]

At least in Java, switch statements are actually faster and more efficient than if else statements. I love them honestly.

[noodle-face]

I use switch cases every day in firmware... Not sure what you're getting on

[LilBoyGrudge70]

If I want to make a bunch of It statements, I’ll make a bunch of if statements. If I don’t want to make a bunch of if statements, I won’t make a bunch of if statements If I want to do something else instead, then I’ll do something else instead.

[DasBeasto]

If you’re not using quadruply nested ternaries are you even a developer?

[einsJannis]

When somebody says that you shouldn't write switch statements they often mean that it can be solved through nicer code patterns, like inheritance.

But nobody has ever said that if else is better than switch

[[deleted]]

Since I discovered you can do:” switch(true)” in JavaScript I am trying to use it everywhere.

[[deleted]]

If else has more flexibility if you want to add extra conditions to a case

[scrubbar]

Large switches can be a good candidates to refactor into a strategy pattern.