Functions Should Be Short And Sweet, But Why?

http://sam-koblenski.blogspot.ru/2014/01/functions-should-be-short-and-sweet-but.html

by AndreyKarpov • 13 years ago

73 65 13 years ago

sam-koblenski.blogspot.ru

sdegutis• 13 years ago

On the flip side, I've seen people take this to the extreme. They often separate lines of code that intrinsically belong together, necessary parts of an algorithm get spread around for no other reason than to try and keep functions small. It leads to code that's really hard to work with and somehow more brittle than when it started.

I'm not saying this happens all the time. But I'm more concerned about it, because I see it more often than the inverse, and it's more damaging to the codebase. At least long spaghetti methods can be refactored into something nice. This kind of mess has to be refactored into a single area first, which is much harder.

cclogg• 13 years ago

Yeah I do hate it when trying to follow through code and I'm having to do searches to find where the next method calls out to in a massive chain of tiny methods. But both sides have their point heh.

I wonder if it's a limitation of our IDEs using plain text and files. Maybe the next generation of programming languages will be nodes or visual blocks that chain together or something? Who knows haha.

Geee• 13 years ago

Check out NoFlo http://noflojs.org/

fuzzix4• 13 years ago

Maybe the next generation of programming languages will be nodes or visual blocks that chain together or something

The problem is, you still need to have control at a "line of code" level of granularity (though not quite a line of assembler mnemonic) if you want to have general purpose programming power. You could probably, with some work, make a graph tool for something like ifttt[0] and do powerful things relatively simply. It's not quite programming though.

I've used state machine UML code generation systems in which you "program" by moving blocks around (something akin to a flow chart). Even when the system's purpose is something extremely limited, e.g. handling a phone's menu transitions, there's still a mind-bending amount of complexity to handle.

I believe ImageJ[1], a freely downloadable image analysis tool, is among the tools with this sort of UML functionality built in if you want to play with it.

[0] https://ifttt.com/

[1] http://rsbweb.nih.gov/ij/

robin_reala• 13 years ago

Scratch? http://scratch.mit.edu/

shangxiao• 13 years ago

Yes code cleanliness would be something like a spectrum where there are instances of extremes on both sides.

collyw• 13 years ago

I am glad to see i am not the only one that finds tons of small methods / functions, with no obvious path through them makes code difficult to read.

tunesmith• 13 years ago

I think some of the perception of how extreme it is has to do with what IDE the coder is using. For instance, in IntelliJ I can have the mouse on a method name and hit a keystroke to go to that method definition, and then another keystroke to go "back" to where I was. That's really helpful for jumping around and following a logical train of thought that goes through several small, one-concept methods - even across files. But, if I were having to deal with an IDE or editor where I was having to string-search and scroll, it'd be maddening and I'd wish for longer, more self-contained (multiple-concept) methods.

gbog• 13 years ago

There is another way, we do not need to be either in a big spaghetti blurb or infinite micro onions spread all over the place in multiple files.

With some work and some luck:

- all functions are short enough but all of them do something more than just passing things around.

- there is never any ambiguity on where a function's implementation is to be found. (In Python, I prefer "import x.y.z" then "x.y.z.myfunc()" than using "from x.y.z import myfunc", for this reason)

- like-minded functions are grouped together.

- functions are nice enough (read: testable and tested enough) so that there is rarely a need to check its code to use it.

henrik_w4• 13 years ago

I have the same experience. I coded C++ in Emacs for many years, then switched to Java in IntelliJ IDEA. I definitely write shorter methods now in Java, than I did in C++ (and it's for the better in my opinion). Navigation in general really is so much better in an IDE. More details in "Programmer Productivity: Emacs versus IntelliJ IDEA" http://henrikwarne.com/2012/06/17/programmer-productivity-em...

mironathetin2• 13 years ago

>On the flip side, I've seen people take this to the extreme.<<

indeed, I have seen functions that contain only one line of code. Even if that is intended for reuse, it makes no sense, because the function call is one line too. Readability goes down the drain this way.

If a reader tries to understand a logic and thinking has to be interrupted by searches and trying to find the right code window, split-ups don't do good things.

Polymorphism, if applied wrong, is a notorious tool to hide the logic from the readers too. If the code decides at runtime, which implementation is used, comments become really important. Especially when this decision is made completely elsewhere in the code. Think strategy pattern, for example.

The underlying problem is IMHO developers blindly following rules. This can be seen a lot. If you ask them 'why' and you get a textbook answer, be careful.

chongli2• 13 years ago

Depends on the language. In Haskell function calls are extremely lightweight, syntactically speaking, and so it's actually quite common to write one line functions. A one-line function may consist of a composition of a dozen or more other functions and be given a short, one-word name. This makes perfect sense for reuse. Or it can be something as simple as this:

    odds = filter odd

While that might not make sense if you only call odds once, you might end up calling it a dozen times! You may also want to limit the scope of this function definition by using a let or where clause. This can aid readability if it allows you to avoid repetition.

amag• 13 years ago

> indeed, I have seen functions that contain only one line of code. Even if that is intended for reuse, it makes no sense

IMHO it can make a lot of sense. In many cases you can clearly specify the intention of that one line by putting it in a function with an appropriate name. Just look at the example from the OP:

void HandleNop() { SPIDataPut(SPI0_BASE, HOST_REPLY_POSACK); }

When you want to handle a NOP, you're not interested in how that NOP is handled, you just want it handled...:)

InclinedPlane• 13 years ago

There is nothing wrong with a one line function. Nothing whatsoever. There are huge benefits to extracting a single line of code into a function. I'll just link to a stackoverflow answer I made on the subject several years back: http://stackoverflow.com/questions/785145/one-line-functions...

Summary: Performance almost certainly isn't an issue (compilers are smart). Abstraction leads to better design, using a well-named function can improve readability, making it easier to understand, easier to prove correct, and easier to modify. When you keep code inline it increases the inertia of the given design and implementation, extracting even a single line into a function (when warranted) can make it far easier to drastically change implementation. And if you want that single line of code to become several lines, or to switch to calling out to a web service, implement caching, add error checking or what-have-you that's made much easier when it's encapsulated inside a function than when it's sitting inside a block.

Componentization is always good, even when the components are sometimes very small. Like all design choices extracting code into its own function requires judgment based on experience but when done right it can have many benefits, even when it's a single line, even when it's a fraction of a single line.

Blindly following a rule such as avoiding making functions too small is just as big an error as avoiding making functions too large.

yummyfajitas• 13 years ago

A single line function makes sense because it allows you to alter functionality later without worrying you forgot about some instance of that pattern:

    def logUnexpectedError(t: Throwable) = log.error("Oops: {}", t)

After I get it together and start keeping proper metrics:

    def logUnexpectedError(t: Throwable) = {
      log.error("Oops: {}", t)
      statistics.errorCounterByClass(t.getClass()).inc()
    }

mironathetin2• 13 years ago

I see, you provide many counter examples for a valid one liner. Indeed, these are good points.

Thats the beauty of a forum, if used in a productive way :o).

pdpi• 13 years ago

A one-line function is perfectly fine (in fact, it's a good sign!), as long as you're translating domain-specific function calls to implementation-specific one-liners. It means your underlying implementation maps well to the problem.

mattmanser• 13 years ago

Best way I've seen code like this described is Holographic code:

http://www.johndcook.com/blog/2012/01/09/holographic-source-...

It's as much a nightmare to work with as overly coupled code is.

agumonkey2• 13 years ago

Funny, I've seen explanations like that for why natural language is full of redundancies. I used to want full DRY/zipped code but I understand the issues better.

e12e2• 13 years ago

I think it (at least in part) depends a bit on the language.

When I tried to solve some simple Java exercises with classic Literate Programming (noweb[1]) -- I found that it helped enormously with simple top-down design -- but I ended up with pieces of code that were a lot smaller than the natural java abstractions -- it felt natural to factor out parts of loops etc... mostly this was me overusing the power that comes with literate programming -- but if done reasonably it could also be rather effective.

It allows one to start essentially with pseudo-code -- but that pseudo code often ends up dealing with stuff like arrays, that with (classic, pre-iterator) java implies explicit counter-variables (like "i") to keep track of an array pointer. So you suddenly get a problem reusing blocks of code, for an inner loop that indexes by "j".

At the same time it made for wonderful compact and readable code (where "code" means the Literate Programming document, not the actual java noweb emitted).

[1] http://www.cs.tufts.edu/~nr/noweb/

lucaspiller• 13 years ago

I've been doing this in client side Javascript for the last year or so. Rather than having 20 lines of nested jQuery callbacks on a page, I make each callback a function and group the event bindings together:

e.g.:

    var showPreview = function() { ... };
    var calculate = function() { ... };
    $('a.preview').click(showPreview);
    $('a.calculate').click(calculate);

Even nicer is to split this out into a separate CoffeeScript file. Then just call `new SuperAwesomeCalculator()` on the page.

I think what made me do this was Erlang. After a point it gets annoying to type NewNewNewNewNewParams, so it's easier just to split it out into a separate function :)

cdelsolar• 13 years ago

I recently started messing around with Clojure, and I love the language. I noticed that you are pretty much basically forced to write lots of short functions if you want to stay idiomatic and readable. It is pretty good in a way.

lstamour• 13 years ago

This reminds me strongly of some concepts I've heard of in TDD Ruby circles though I'm certain they're not unique to that. The bit on writing your function names first is like the practice of "write the test with the API you want to use, then make it pass with an implementation that does just that." It's a kind of planning-by-wishful-thinking that just seems to work in certain scenarios. But I think for it to be successful, you need to read enough best-practices code in your target language to understand better approaches. That said, using your phantom code first will give you a better API design. The trick, as in this article, is to keep writing ideal implementations like turtles all the way down. If your logic is complicated enough that you'll need notes or comments, descriptive function names are wonderful. Particularly in languages like Objective-C with named parameters.

cheapsteak• 13 years ago

I've thought about it as the programming equivalent of writing outlines before starting on an essay. It requires more forethought, but you can recognize early on if a line of thought / solution is a dead end, and also makes restructuring and fixing it much easier

henrik_w4• 13 years ago

I often end up factoring out things into common methods in the end. That's when I see what parts are common, something I don't always recognize in the beginning (or even in the middle of it).

chipsy• 13 years ago

I think it's a Goldilocks problem. There's an optimal average size for any group of related functions, but the skill of planning it is not in nailing it on the first try, but in determining whether the refactoring will benefit more when the initial estimate is padded higher or lower.

The main reason for going small at first, I think, is that it creates more names. Names especially help with very simple calculations that appear repeatedly and turn into visual noise(true of a lot of UI code). The naming process can point you towards an instant design change as you discover what you are "actually" doing in the code. A big function acts as a bigger black box, thus it can hide these issues. Sometimes you want the black box, but it's the exceptional case.

henrik_w4• 13 years ago

I completely agree - I made the same points in "7 Ways More Methods Can Improve Your Program" http://henrikwarne.com/2013/08/31/7-ways-more-methods-can-im...

dschiptsov• 13 years ago

This is why decent schools in old days taught students Lamda Calculus and Scheme or even Haskell. It helps do develop a strong aversion to verbose spaghetti code very early.)

rtpg• 13 years ago

I think most design patterns and 'best practices' exist because, without them being explicit, people will tend to do the opposite. Obviously, there are always use cases where going against the pattern might make sense. But you should be able to justify it.

Would you rather have mostly short functions with a couple long ones or the opposite?

chj• 13 years ago

All the reasons boil down to one: human brains can not hold too much working memory.

taeric2• 13 years ago

Is it a form of irony when programs wind up overwhelming this memory with too many functions? :)

AnimalMuppet• 13 years ago

Where do you spend your time? I spend some of my time trying to find the right function, and that gets harder if there are more functions. But I spend more of my time trying to understand and/or modify that function, and that gets easier with smaller functions.

So more, smaller functions winds up being a net win (up to some limit, of course...)

cheshire_cat• 13 years ago

My (quite oldschool) professor taught me about this top-down design. This kind of "write as if you have all the methods you want/need" style is sometimes called "Wishful Programming" http://blog.thesoftwarecraft.com/2013/11/wishful-programming...

Bart Bakker references "Structure and Interpretation of Computer Programs" as an early source and I'm somewhat positive that I read about an similar approach in "How to design programs 2nd ed", called "programming with a wish list".

Edit: I found the mention in HtDP but as I understand it it's not exactly the same as wishful programming: http://www.ccs.neu.edu/home/matthias/HtDP2e/part_one.html

under "3.4 From Functions to Programs"

agumonkey2• 13 years ago

I remember doing something similar in college using Eclipse/Java (but any static analysis friendly language with on-the-fly type checker would do) and it was pure fun. You just write the code as you'd want it to be, the IDE will flag missing classes/interfaces and generate them on the go if you tell them, and if down the road you use one interface differently the IDE will extend or ~reparameterize it for you. You end up with an abstract system/algorithm that works by type checked interfaces you can now implement.

NicoJuicy• 13 years ago

For everyone that didn't knew this, http://amzn.to/1hhI37v

You should read it..

PS. It's the book Code Clean ;)

yason• 13 years ago

Functions should be short and sweet, to an extent, because by thinking in terms of functions you're building a new language in which you write your program.

If you're writing big functions by habit then you're just laying more code after existing code to build a program. If you split your code in functions and, instead, start talking in the language you've just invented then you're composing a program. And I think compilers should do the building while I refrain myself to composing.

Of course, one-line functions don't have inherent value but sometimes they're needed. For example, to present a higher-level concept that just effectively happens to be a simple assignment or an inc.

Short functions themselves don't have an inherent value either: if you manage to write your function with less tokens, possibly due to composing it out of other functions, then that's all good but isn't the real value of doing it. Shortness for the sake of shortness only matters until you're down to a screenful or so.

The real value of defining and writing functions is thinking of the proper words for your language. As soon as you're making your own language, then you're just using functions as vehicles to represent words in that language. Some words might take 30 lines to code, some words might take 3 lines. It doesn't matter as you've got your language together in a way that is concise and beautiful which is the real point.

jboy• 13 years ago

This is an excellent answer, and (in my opinion, at least) really gets to the heart of the matter.

I'm not unduly obsessed with classes or design patterns in object-oriented languages, but to me the key benefit of functions, classes and design patterns is about defining a shared language of named abstractions.

These abstractions take care of details, so you can think at a higher level. The names are a common vocabulary shared between the designer/implementer and user/client of the code; and as yason says, if you choose your abstractions at an appropriate level, you can "talk about" (or describe/define) the problem+solution in terms that are best suited to the problem+solution.

And to note one more benefit of short functions: When you're talking about functions (operations) and classes (encapsulated state), you rely upon these abstractions to behave in a certain way. Shorter functions and simpler classes generally have fewer moving parts, thus making it easier to verify the correctness of the implementation of the abstraction concept.

sergiosgc• 13 years ago

Excellent answer. Another view (dual and equivalent) is that you are climbing the abstraction layer. You should do it with clean abstractions, that do not leak. It's easier to write clean abstractions if they are limited in scope, so it is better if each function does one thing and does it well.

TeMPOraL• 13 years ago

Right to the heart of matter.

This is something Abelson & Sussman were trying to teach us in the 80-s (stacking abstractions-as-languages on top of each other is one of the main themes of SICP). Unfortunately this insight got somehow lost in between people parroting design patterns and repeating things without understanding them (programming pop-culture?). I've personally seen only a handful of programmers who know of this concept, and even less of folks who understand it.

aufreak3• 13 years ago

I disagree with supporters on the value of this comment and of the OP as well.

Though the naming seems to give documentation benefits, naming variables and functions is one of the hardest things we do as coders. The practice of properly factoring your system comes more out thinking in terms of values rather than steps. When you think "what value am I computing?", you not only write short sweet functions naturally, but also build more robust code in the process.

And yes functions are values as well.

e12e2• 13 years ago

Great comment. This also fits nicely with vpri.org's work on 20KLOCs for the whole system (possibly including logic gates). I'll just borrow this other great comment on vpri that I found googleing for the approriate vpri.org link:

https://news.ycombinator.com/item?id=3292663

jbeja• 13 years ago

This comment make so much sense to me.

kingrolo• 13 years ago

I worked on a massive codebase once many years ago (C#/.NET) which had been built by a relatively competent outsourced team. Somewhere along the way some consultant on the UK side of the business had insisted that each function could be no more than 5 lines long. It was horrible to work with - it took so long to find the place you actually needed to make changes, and it seems like they'd just started inventing layer names in order to facilitate it.

So yeah, small functions good, but you can take it to extremes.

sigmaml• 13 years ago

I worked on a similar project; the US consultant insisted that each method should be less than 25 lines. The code involved several decision trees. This rigid limit made the code quite inconvenient to follow and enhance. After much sweat and swearing on both sides, the limit was increased to 40 lines!

lostcolony• 13 years ago

I've run into that.

Compounding that issue, I've run into cases where people pulled out code into functions, realized that in two places the behavior was ~slightly~ different, and they addressed it by adding a variable, 'shouldThing' or something, that serves just as a boolean flag as to which bit(s) of logic you should fire. So now rather than just have to focus on the code that needs changing, I've got to go to an entirely different section/file, and wade through code that doesn't even relate to what I'm trying to fix.

noir_lord• 13 years ago

Functions Should Be Short And Sweet, But Why?

In my case the why (as well as many of the arguments here) is because I'm not a "superstar/rockstar ninja coder" and by keeping functions short, clear and with a descriptive name in 6 months when I open the file to fix the change request I won't have to spend 2 hours building a mental model of the system to fix the bug.

mercurial• 13 years ago

If your rockstar coder makes functions five screen longs as a matter of habit, you may consider changing bands.

VexXtreme• 13 years ago

I just had to deal with extending an absolutely massive C++ function the other day and it was a nightmare. The function was 2500 lines long and littered with several dozen exit points - all of which execute under slightly different conditions. Throw in a couple several hundred lines long switch-case statements and you can see what I'm getting at. Figuring out the right place to put a breakpoint that will actually fire due to a maze of conditions and returns took me a couple hours.

Of course, I've seen many cases where people take this to the opposite extreme and start breaking up functionality that logically belongs together and can't be reused in other contexts. It makes it pretty apparent that writing decent readable code is hard (for many people anyway).

virmundi• 13 years ago

"start breaking up functionality that logically belongs together and can't be reused in other contexts"

I know you said you're in the C++ world, so I don't think what I'm doing fits yours, but I've responded to the same behavior in the Java world in a way that tends to confuse and mystify my co-workers. In Java I've started to declare classes within methods. These classes can compute complex processes, but are nicely tucked away in the only logical place they make sense, that method.

My reason for this is that the method really belongs to the containing class. I can't break it down or abstract it out. I could use composition, but the new method-class isn't usable by anything else. The sub steps in the method aren't usable by any other method within the housing class. I could put them there, but they would just muddy the outer class. So now the code looks something like this.

public class Outer { void doSomethingComplex(final params) { class ComplexThing { private void step1() {...} private void step2() {...} public void goToTown() {...} }

    new ComplexThing().goToTown();
  }

}

ComplexThing gets access to the outer params. This cuts down on constructor complexity and cements the intricate bond between the two entities, method and inner class. The logic is broken down nicely. Finally, nothing is needlessly shared.

This might make the outer class a bit larger, but I find this structure pleasant.

It's also a useful pattern for writing tests. Each test method gets a class (could have inheritance) that has a setup, test, tear down. All of that is encapsulated in one place.

JoeAltmaier2• 13 years ago

I know that code. Mine was a serial protocol with a maze of flags and conditions.

I drew a table on a large sheet of paper, and recopied the code as a state machine. When I was done, it was clear where the problem lay: the state machine was woefully incomplete.

I rewrote the thing AS a state machine with all state-event pairs handled. Voila! It worked. Had to go back and diddle with some events (better way to handle parity error during checksum calculation etc) but at least I could find exactly the place in the code to do that.

avdd_• 13 years ago

So why does the main function in this example violate the principle ... i.e. where is the dispatch table?

mildtrepidation• 13 years ago

Functions should be exactly as long as they need to be to accomplish their purpose. The purpose is the important part: A function should have a concise and easily-understood purpose (or very small and logically inseparable set of purposes) and, tangentially, a name that describes it well.

You can have a fairly long function that's readable and maintainable; those last two are the important part, and, to a point, they hinge more on how much work is being done than how much code it takes.

Of course, if you're just plain writing more code than is needed, that's not a problem with the function itself.

JoeAltmaier2• 13 years ago

Yes, the idea of writing straightforward code is critical. If you can do it in less lines, even at expense of speed or space, you benefit many-fold. Its easier to understand, read, explain to someone else, remember, debug, compile. The slowest processor in the system is the wetware between your ears. Funny we rarely talk of optimizing for speed or space in that engine!

Functions Should Be Short And Sweet, But Why?

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