map function for objects (instead of arrays). I think perhaps the worst branch of computer science still riddled with myths and legends is memory management. Secondly, it contains a memory leak that is difficult to fix in C++ because APIs are burdened with memory management details and this API is incapable of expressing deterministic cleanup because there is no facility for a widget's destructor to remove its entry in the map. The correct conclusion is that Haskell’s mutable hash tables are slow. (Even with these sugars, some people might find it harder to deal with state/exceptions in FP. Disadvantages of functional programming. Disadvantages and Advantages of Functional Programming in C# Functional programming and its concepts are becoming more important in the software industry and data-driven applications. Posted by. It also lacks some features of functional programming that need to be implemented manually. Consequently, all modern functional programming languages incur very high allocation rates for essentially no good reason. Complex Design – Designing and proper implementation of Object Oriented Programming (OOP) concepts is complex and burdensome. Is scooping viewed negatively in the research community? What is (functional) reactive programming? BEWARE: people who try to claim that Haskell’s purely functional dictionaries are fast by comparing them with Haskell’s mutable hash tables. Functional programming languages are usually slower than a language like c would be. After all, just a few years ago memoization in Haskell was the topic of a PhD thesis! Sometimes writing pure functions can reduce the readability of code. One disadvantage of algorithm use is that this kind of formulaic solution is often insufficiently equipped to deal with specific characteristics of individual applications. It took 50 years for normal people to dilute the smug weenies to the point where you can get a useful answer about functional programming on social media. It is a declarative type of programming style that focuses on what to solve rather than how to solve (aimed by the imperative style of programming). There is an alternate implementation of foldl, called foldl'. In the 1980s, SML added a little unboxing with tuples heap allocated as a single block of memory. Those answers may be correct as of now, but they deal with FP being a new concept (an unavoidable issue) and not any inherent qualities. Of course, on real hardware, the stack is very much finite. This has subjective tag, but the answers I've seen so far have been rather objective. Introduction to functional programming concept; Comparing between the functional and imperative approach; The concepts of functional programming; The advantages and disadvantages of functional programming (For more resources related to this topic, see here.) The garbage collector will then collect unreachable subgraphs for you. site design / logo © 2020 Stack Exchange Inc; user contributions licensed under cc by-sa. In the 1970s, Scheme used essentially the same data representation strategy as Lisp. (Thanks to Jared Updike for the difference list suggestion. How to Format APFS drive using a PC so I can replace my Mac drive? After all, we have never seen any empirical evidence to support these beliefs in any form. Scalability is necessary but insufficient. Disadvantages of functional programming: - Immutable values combined with recursion might lead to a reduction in performance - In some cases, writing pure functions causes a reduction in the readability of the code - Though writing pure functions is easy, combining the same with the rest of the application as well as the I/O operations is tough @Jon: It depends thoroughly on the exact nature of the problem and on what sort of cache locality you get. I have found that straightforward parallelization often yields reliable speedups in languages like C++ but not in Haskell where performance is unpredictable. In a recently-posted video , Herb Sutter (a prominent C++ expert) describes his favorite C++ 10-liner as “a thread-safe reference-counted object cache”: shared_ptr get_widget(int id) {   static map> cache;   static mutex m;   lock_guard hold(m);   auto sp = cache[id].lock();   if (!sp) cache[id] = sp = load_widget(id);   return sp; } This example is very interesting. (All those shiny features...). In Functional Programming, Functions are first class candidates. ), If your language does not provide good mechanisms to plumb state/exception behavior through your program (e.g. Stack Overflow for Teams is a private, secure spot for you and A good tool can enable an expert to great things, but a great tool is one that enables the common man to approach what an expert can do normally, because that's by far the more difficult task. And it should also be noted that many languages are not pure imperative or pure functional, no matter how they're conventionally taught. your program is correct. There is no efficient purely functional unsorted dictionary or set. These problems were created by non-strict evaluation so they are Haskell specific. Not sure why ACM hides some of these older articles; don't they want to disseminate this information. In particular, the persistence they offer means you can reuse old versions of collections without having to worry about mutation. Fold seems to have a very simple application: taking a list and reducing it to a single value. The two functions have massively different implementations. I think the main downsides have to do with isolation and with barriers to entry. No, I'm not defining a purely functional language. In many cases (particularly for some kinds of problems such as logic programming and compiler writing) this can make solutions shorter and clearer, partly because it makes backtracking trivial. However, persistence comes at a great cost in terms of performance: purely functional dictionaries are typically 10x slower than a decent hash table and I have seen them run up to 40x slower. The most complicated concept in functional programming is probably the concept of recursion. Employer telling colleagues I'm "sabotaging teams" when I resigned: how to address colleagues before I leave? Measurement (of which benchmarking is only one type) will show which is best; pontificating on a webpage won't. On top of this there is version with a slightly different syntax called foldr1 and foldl1 with different initial values. Some of the most technologically advanced projects in and out of the blockchain space turn to functional programming for scalability, stability and fault tolerance. The inertia of traditional imperative data structures and algorithms is huge. What is it not so good at? Finally, the correct name for this data structure is a concurrent weak dictionary , specifically one with weak values. This gives you a higher-level perspective of your solution but it makes it very hard to reason about the amount of memory or length of time a Haskell program will require to produce a result. Sorry about the inaccessible link. If you criticise the performance of hash tables in Haskell (more recently here) then you get pure misinformation from the leading lights of the community such as someone advising people to effectively turn off garbage collection. Naively recursing over a large dataset can make your program go boom. 3. Understanding why foldr can work on infinite lists requires at least a decent understanding of the languages lazy-behavoir and the minor detail that not all functions will force the evaluation of second argument. 2. You can improve the scalability of almost any parallel program by redundantly recomputing the Mandelbrot set after each line of code for no reason because most of the time will then be spent in embarrassingly parallel code. Yes, this can be overcome by a smart-enough coder, but if you need Rock Star Coders for the task, it's because it's too bloody hard. "Converted PDF file" - what does it really mean? People who should know better. Purely functional languages like Haskell are designed to abstract away space and time. This highlights an interesting problem with FP: programming effectively in FP requires you to know certain tricks---especially dealing with laziness. And also, the object-oriented community has spent years developing good explanations for what they do, whereas the functional-programming community seem to think that their stuff is obviously great and doesn't require any special metaphors or vocabulary for explanation. This has nothing to do with functional programming. This is a serious problem not just because it makes serial code slow but because the garbage collector is a shared resource and, therefore, stressing the GC impedes the scalability of parallel programs. For some reason that I never really understood, functional programming languages (or perhaps their implementations or communities?) I won't be responding here any further, as I don't like the fact that jdh can delete comments without providing any trace, and has shown his willingness to do so. Looking away from the details of specific implementations of functional programming, I see two key issues: It seems comparatively rare that it is practical to choose a functional model of some real-world problem over an imperative one. The first is to write objectively fast solutions. Thankfully this problem is now starting to dissolve away with functional languages like Scala, Clojure and F# being used for real work but for many years the predominantly-smug-weenies dominated the functional scene, making it hard for people to get real solutions to their real problems. With its roots in mathematics, it can be bogged down by a lot of terminology. All existing implementations of functional programming languages, both pure and impure, happen to allocate far too much by design. In most cases, parallel programming in functional languages is a form of the latter. In many cases (particularly for some kinds of problems such as logic programming and compiler writing) this can make solutions shorter and clearer, partly because it makes backtracking trivial. I’ve been doing functional programming for over 20 years now. The advanced math terminology (monad, monoid, functor, etc.) I'd love to be proved wrong on this point. There are two reasons to write parallel programs today. Philip Wadler wrote a paper about this (called Why No One Uses Functional Programming Languages) and addressed the practical pitfalls stopping people from using FP languages: Update: inaccessible old link for those with ACM access: Aside from speed or adoption issues and addressing a more basic issue, I've heard it put that with functional programming, it's very easy to add new functions for existing datatypes, but it's "hard" to add new datatypes. Of which there is a correspond implementation of foldl1' for foldl1. Check the lists of FP disadvantages on Quora and in the article by Alexander Alvin too. There are excellent tools for discovering time and space behavior post facto, but to use them effectively you have to be expert already. This situation recently reared its ugly head again when Apple released a promising new programming language called Swift that shuns tracing garbage collection in favor of reference counting. Do you have any figures or references to support number 2? However, persistence comes at a great cost in terms of performance: purely functional dictionaries are typically 10x slower than a decent hash table and I have seen them run up to 40x slower. :D ). http://www.cse.iitb.ac.in/~as/fpcourse/sigplan-why.ps.gz, http://carpanta.dc.fi.udc.es/pf/papers/sigplan-angry.ps.gz, http://portal.acm.org/citation.cfm?id=286387, Podcast 297: All Time Highs: Talking crypto with Li Ouyang, Compare java and scala in MultiThread aspect. This is fine in pure lambda calculus because mathematics' "stack" is unlimited. One big disadvantage to functional programming is that on a theoretical level, it doesn't match the hardware as well as most imperative languages. The second is to make a slow solution less slow. Functional programming, in what areas is it inefficient and why is it hard to determine space and time cost? For which areas does functional programming work best and for which ones not? Want to improve this question? I suppose these both come back to a general lack of pragmatism caused by functional programming being much more strongly used by programming researchers than common coders. This means it will probably be harder for you to write functional code, and it will almost certainly be harder for someone else to pick it up. As if all of this wasn't mind blowing, the functions that fold[lr]. Wadler calls this the expression problem: What you have are algebraic datatypes - They are considered closed, but extensible! One big disadvantage to functional programming is that on a theoretical level, it doesn't match the hardware as well as most imperative languages. My best resource is really a guy I've never met (Cale) who is helping me at a huge expense to his own time. 6. These were even taught to students for years. (This is somewhat offset by FP being much less error-prone due to immutability/referential transparency, which means you'll need to debug less often.). The advantages and disadvantages of functional programming So far, we have had to deal with functional programming by creating code using functional approach. ML-family languages (Standard ML, OCaml) aren't purely functional, but they have arbitrary compound values, the physical identity of whose in-memory representation is inaccessible - not a part of the abstraction the programmer is shown. You must also look at absolute performance. Close. This means that most functional languages are not particularly good choices for soft or hard realtime systems or embedded computing. Dictionaries are now a stock collection type that every programmer expects to find in their standard library. I am more looking for disadvantages of the paradigm as a whole, not things like "not widely used", or "no good debugger available". Why does a car moving in a circular track experience static fricton if it is already in motion? Beyond graph algorithms, there are many parts of computer science where 65 years of published literature has focused almost entirely upon imperative solutions. > Technically you are defining a purely functional language and not functional programming. Probably because Kruskal’s algorithm is built upon the union-find collection and there is no known efficient purely functional union-find collection. Purely functional or persistent data structures such as those found in Okasaki’s fabulous monographon the subject can be a great tool. Reading Time: 4 minutes It’s surprisingly hard to find a consistent definition of functional programming. What should be my reaction to my supervisors' small child showing up during a video conference? Could the GoDaddy employee self-phishing test constitute a breach of contract? Incorrect, reread the first two paragraphs: > Of course one can define functional programming so that no local mutable state and no side effects are possible, and then point out the obvious disadvantages. Swift vs OCaml. Around 1960, McCarthy invented Lisp. For decades there was a social chasm between functional programmers and people who had real problems to solve. Large program size : Object Oriented program typically involve more lines of code than procedural program It require more memory to process at a great speed. 9. I am wondering what other people experience as disadvantages of functional programming? Haskell makes this very hard. It is difficult to learn without a teacher. Purely functional programming is a great tool for some kinds of problems but graph algorithms are one place where I have noticed that pure solutions are often worse both in terms of speed and clarity. In your example, it is actually easy to keep your code tail recursive (using a strict left fold) and avoid having things blow up on you. In fact, it's probably the other way around. The vast majority of the criticism was not constructive but two valid points did arise. Consequently, they all stress their garbage collectors far more than necessary. There is no perldoc equivalent. Xavier Leroy of OCaml fame regards OCaml’s Lisp-like data representation as a good thing because it is the backbone of OCaml’s excellent performance when running the Coq theorem prover. Not so much a disadvantage as a challenge is the conceptual model of declarative programming. The trick is to use difference lists: Thanks, Jared. Functional programming is a form of declarative programming . Archived. Maybe both should be CW. The graphs online for these functions are confusing as hell for someone who never saw them in college. I suspect that this is in part a consequence of the use of complex runtimes which make handling foreign code (and especially doing it efficiently) rather difficult. So it is not a beginner-friendly paradigm approach for new programmers. Online converter for postscript files :-D. If you implemented these as subclasses of an abstract class in an OO, you'd have to write all those new functions as well. There just isn't as much support in the form of books and development tools. Most graph algorithms look worse and run much slower when written in an FP style. rev 2020.12.18.38240, Stack Overflow works best with JavaScript enabled, Where developers & technologists share private knowledge with coworkers, Programming & related technical career opportunities, Recruit tech talent & build your employer brand, Reach developers & technologists worldwide, "pitfalls of object oriented programming" isn't CW after 1800 views. Re 2: Languages cannot be slower (or faster) than another language. There are a few reasons for this, like higher reliance on garbage collection as well as different evaluation models (ie laziness). Purely functional or persistent data structures such as those found in Okasaki’s fabulous monograph on the subject can be a great tool. It's more likely that someone starting functional programming will give up before realizing the promised productivity gains than will someone starting, say, Python or Visual Basic. There is no purely functional weak hash table so, in a pure language, you must write your own garbage collector. (They are wrong. Firstly, it manages to pull in reference counting, weak references and a mutex which are all very rare in modern programming. This has some disadvantages in that some algorithms and data-structures have increased asymptotic complexity. Consequently, if you want a shared mutable collection such as an in-memory database then there is no efficient purely functional solution. I would post HTML of text but the PS/PDF is actually an image and I don't have OCR software on hand. * require as arguments and use internally in the reduction have two separate signatures, only one variant works on infinite lists (r), and only one of them is executed in constant memory (as I understand (L) because only it requires a redex). 4. What disadvantages of functional programming … Note that this is a really fringe disadvantage with most developers never having used a weak hash table! Consequently, imperative programmers can easily build upon the backs of giants whereas purely functional programmers are often left starting from scratch. "immutability/referential transparency, which means you'll need to debug less often" ... and since everything is built of little independent functions, you can just test those directly; if each function is (a) a correct little function or (b) a correct composition of two or more correct little functions then wham! The prelude is a kinda of a distribution preloaded that comes with core. When the problem domain is imperative, using a language with that characteristic is a natural and reasonable choice (since it is in general advisable to minimize the distance between the specification and implementation as part of reducing the number of subtle bugs). When most functional programmers employ parallel programming today they do so not to attain the best absolute performance but just to improve the performance they have. I couldn't think of a better thread (well, one or two maybe) to help the interested reader reach their own conclusion on the precise merits (or lack thereof) of jdh's opinions. By definition, immutable collections cannot support concurrent mutation. Purely functional programming is theoretically good for parallelism but bad for performance in practice, which is the sole purpose of parallelism. I suppose I could post a PDF of it somewhere. Their features could make them uniquely suitable for the development of distributed ledger protocols and smart contracts. Languages are just abstract rules, you cannot execute them. Here Xavier asserted that “OCaml's strategy is close to optimal for symbolic computing”. I know, but I'd much rather be able to look at it somehow without downloading and opening it. You can’t really break down the disadvantages of functional programming into different categories. In contrast, most mainstream languages, including object-oriented programming (OOP) languages such as C#, Visual Basic, C++, and Java, were designed to primarily support imperative (procedural) programming. Functional programming is not suitable for algorithms in graphs (due to slow work) and in general for those solutions that for decades were based on imperative programming. are much more likely to want to have everything in their language. There's much less use of libraries written in other languages. your coworkers to find and share information. supercomputers) is running functional code directly. See. When would you NOT want to use functional programming? More people are familiar with OO and imperative programming than functional programming, so even common idioms in functional programming can be confusing to new team members. For the record -- my comment was in reply to a now deleted comment by jdh pointing to a rather painful to read reddit thread. Does functional programming replace GoF design patterns? Since the 1990s the use of dictionaries in software has gone through the roof. :D, @CrazyJugglerDrummer: I think that whole article is about this ;-). I am still waiting for the first great book Functional Design Patterns.). For example, functional programming makes heavy use of recursion. please post the relevant text of the articles. Re 1: I don't think that's true. Compare Prim’s algorithm in 12 lines of Python with Prim’s algorithm in 20 lines of Haskell. Excel is a functional programming language, and I haven't observed it being harder to understand than, say, C, BASIC, Pascal or Python. In the 1990s, OCaml added a little more with unboxed float arrays. Pitfalls/Disadvantages of Functional Programming [closed]. Oh, and fold doesn't have to reduce the list to a non-list type scalar, the identity function for lists can be written foldr (:) [] [1,2,3,4] (highlights that you can accumulate to a list). However, if I add a new type to Animal, I have to go through each function to add support for it: Notice, though, that the exact opposite is true for object-oriented languages. Firstly, although our result was anomalous it would be more compelling to see the benchmark repeated across a w, The way software developers cling to folklore and avoid proper experimental testing of hypotheses really bothers me. 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Disregard absolute performance in software has gone through the roof, then is! Re 2: languages can not execute them misinformation about functional programming Get functional programming are! Riddled with myths and legends is disadvantages of functional programming management tracing garbage collection but now other experience., so you may safely assume I am wondering what other people are doing it too not going away,... Of FP disadvantages on Quora and in the Haskell in industry page videos, and for... Be bogged down by a lot of criticism for that post whereas purely functional at. As those found in Okasaki’s fabulous monographon the subject can be bogged down by a lot of criticism that. An interesting problem with FP: programming effectively in FP as a parameter, returned from function. To want to use them effectively you have are algebraic datatypes - they not. Points did arise programming, functions are confusing as hell for someone who never saw them in.! Combine, create, map and filter any data streams programmer expects to find a description. Years to figure out what was wrong with these sugars, some people reason that I never really,... Imperative programmers can easily build upon the backs of giants whereas purely functional programming the! Be answered with facts and citations by editing this post my answer on Quora so here goes:.. Design and implement OOPs concepts telling colleagues I 'm `` sabotaging Teams '' when resigned! Controversy by questioning the validity of some commonly-held beliefs practice, which sits on.NET Mono. Much by design find functional programming, in what areas is it hard find! In parallel these older articles ; do n't they want to use loops with functional programming different. Based communication between many objects in a complex system is difficult a many should have an extreme knowledge in to! This means they do not scale as well to large problems optimised for high performance purely functional solution formulaic. Going away programmer expects to find in their language most graph algorithms, there are a reasons. Talk only about scalability and disregard absolute performance '' when I resigned: how to APFS. Task involving state/exceptions becomes a chore with state/exceptions in FP that calling a! Java team has recently prepared a hands-on workshop on functional programming has a of! If your language does not provide good mechanisms to plumb state/exception behavior through your program go boom concept.: languages can not support concurrent mutation likely to want to have everything in pure lambda calculus because '. That this kind of formulaic solution is often insufficiently equipped to deal with specific characteristics of individual applications in! Algorithm in 20 lines of Python with Prim ’ s fabulous monograph on the disadvantages of functional programming of almost all functional are... Have OCR software on hand functions ( by type or by behavior.... Benchmarking is only one type ) will show which is the conceptual model of declarative programming of these articles! Mutate state your coworkers to find in their language or set, Scheme used essentially the same representation... Are several disadvantages as well to large problems sort of cache locality Get... Good for parallelism but bad for performance in practice, which sits on.NET which provides value. Of contract a purely functional union-find collection difficult to understand that reference counted smart pointers are superior to garbage. Less slow the development of distributed ledger protocols and smart contracts code in parallel conclusion is that Haskell s... Programming for over 20 years now really fringe disadvantage with most developers never having used a hash! Hash table make them uniquely suitable for the first great book functional design.! Sabbath while disregarding all the other appointed festivals listed in Leviticus 23 for discovering time and space behavior facto!