8 ms·

Best example I heard was in an F# talk. The guy used a bar tending analogy: FP => I'll have a Sazerac Imperative => Excuse me sir, could you take some ice, ad

Best example I heard was in an F# talk. The guy used a bar tending analogy: FP => I'll have a Sazerac Imperative => Excuse me sir, could you take some ice, add rye whiskey, add bitters, add absinthe, shake, strain into a glass, and add a lemon garnish before bringing it to me

owyn 10y ago
FP is more like: drink(sazerac(garnish(strain(shake(absinthe(bitters(whiskey(ice(glass))))))))) Ultimately it's the same result? The difference is when you can reuse and compose functions.
- threeseed 10y ago
  Exactly. FP you start with the methods and just keep composing. With OO you start with classes and objects.
  - Chyzwar 10y ago
    In OOP you compose nicely as well. It is also easier to understand because it is just conversation. Me(Drinker)->drink( Sazerac(Cocktail) ->garnish() ->strain() ->shake() ->absinthe() ->bitters() ->whiskey() ->ice() ->glass() )
    - sooheon 10y ago
      If you want to create a bar food (Finger Food object, not Cocktail), which also could use a garnish() method, which inherits from which? Or should both objects have a father, Garnishable object to inherit from? It's clear to me that object composition is less flexible than functional composition.
      - kuschku 10y ago
        You just have the method as an aspect that you import into the class ;)
      - Chyzwar 10y ago
        You can have trait/interface. But since garnish will be doing different thing it is OK to have two implementation. FP looks nice in theoretical examples in real world not so much. In FP you will end with garnishFingerFood and garnishCocktail because you need to encode somewhere a specifics of garnish action. In OOP you will have garnish methods on Coctail and FingerFood and specifics and related knowledge how you need to perform garnish will be on object itself. OOP is really powerful concept but failing in languages that have shit implementation. Java, C++ forsake OOP principles for "performance" or are made by people that do not understand concepts (Python, PHP).
        leshow 10y ago
        From the specific example you're presenting, I don't see how you couldn't just have a Garnishable typeclass, that implements garnish differently for the FingerFood or Cocktail types. The comment that FP isn't nice in the real world is pure baloney. For lots of "real world" IO-bound types of problems there is nothing better suited than a functional programming language with powerful abstractions. Things like monads let you write code in an imperative style without losing any of the benefits of writing in the functional paradigm.
        dpkp 10y ago
        > In FP you will end with garnishFingerFood and garnishCocktail because you need to encode somewhere a specifics of garnish action. In OOP you will have garnish methods on Coctail and FingerFood and specifics and related knowledge how you need to perform garnish will be on object itself. You're complecting. In the real world of Clojure, you could simply define a protocol and provide different implementations of "garnish".
        yawaramin 10y ago
        OOP doesn't actually have the market cornered on polymorphism. As my sibling replies show, FP languages have long known how to achieve it.
      - junke 10y ago
        Generic functions: functional yet dynamically dispatched.
        jeremiep 10y ago
        Generics aren't dynamically dispatched. Java has type erasure and C# emits variants for every instance.
        junke 10y ago
        No, I was talking about (Common) Lisp's generic functions (http://clhs.lisp.se/Body/m_defgen.htm http://clhs.lisp.se/Body/m_defgen.htm). I realize I did not give enough context. Define a generic function: (defgeneric garnish (what with-what)) Specialize it on one or multiple arguments: (defmethod garnish ((c cocktail) (f fruit)) ...) (defmethod garnish ((s sandwich) (h ham)) ...) ... But you can use it like a function: (let ((currified (rcurry #'garnish :curry))) (map 'list currified items))
        jeremiep 10y ago
        Ah my bad! :) These look very much like Clojure's protocols and multi-methods.
        junke 10y ago
        Yes, more like multi-methods, except for standard qualifiers (:around, :before, ...) and user-defined ones. OTOH, Clojure allows you to define a custom dispatch function.
        jeremiep 10y ago
        Ah yes, Clojure has no first-class support for aspects. Its easy enough to monkey patch definitions for the rare case when its needed. Most of the time however I try to avoid aspects as they introduce hidden behaviour in existing functions, which can be hard to reason about at scale, especially with more than a few developers.
    - fnordsensei 10y ago
      I would probably use threading to achieve comparable readability. (def sazerac (-> (mix :ice :whiskey :bitters :absinthe) shake strain garnish)) (drink :me sazerac) I never had a Sazerac. It sounds like a nice drink.
      - greydius 10y ago
        I would create a Cocktail data structure and an instance of Monad for it. sazerac = do add ice add ryeWhisky add bitters add absinthe shake strainInto glass add lemonGarnish main = serve $ makeCocktail sazerac
        dllthomas 10y ago
        Haskell really is a pretty nice imperative language sometimes.
    - yomly 10y ago
      And people have the cheek to complain about parens in Lisp...
      - jeremiep 10y ago
        Its ironic because foo() and (foo) have the same number of characters; but the later is actually data you can manipulate directly. Reminds me of the blub paradox in beating the averages[1]. [1]: http://paulgraham.com/avg.html http://paulgraham.com/avg.html
      - mahyarm 10y ago
        I once had a comment where I translated a clojure function into it's equivalent syntax in python. It was still pretty hard to read. I think its about how lisp uses function composition for everything makes code hard to parse until you get good at it. Even with the standard practice is to hide it with macros and many small functions. https://news.ycombinator.com/item?id=11174946#11177360 https://news.ycombinator.com/item?id=11174946#11177360
        bpicolo 10y ago
        I like more forward-building, pipe style FP. Reading outwards on the statement level still makes things hard for me.
    - dustingetz 10y ago
      fluent interfaces from OOP are different than composition because they mutate-and-return the object reference; if the instance is aliased anywhere else in the program there is spooky-action-at-a-distance. Composition is about programming with values without mutation. As far as syntax goes it is a trivial macro to translate `x.f().g()` into `g(f(x))` (clojure actually provides it : http://clojure.org/guides/threading_macros http://clojure.org/guides/threading_macros)
      - yawaramin 10y ago
        > they mutate-and-return.... Not necessarily; you can easily write instance methods which merely copy the existing object.
    - jeremiep 10y ago
      That isn't composition to me but sequencing. Function composition yields a function, not the result of applying the functions. Either you have an object with all of garnish(), strain() and whatnot on it, or each method returns the object to handle the next step in the chain. Either methods don't scale at all without modifying existing code. The real difference is that function composition gives you a reusable function you can further compose while objects keep piling up methods until you're left with god objects or indirection hell.
junke 10y ago
The example is just about abstraction. The imperative equivalent would be: "Give me a Sazerac!" (imperative, hehe)
- dllthomas 10y ago
  "It is imperative that you give me a Sazerac!"
  - junke 10y ago
    Some time ago at University, we had to develop a puzzle solver in FP. In the report's introduction, I wrote something like "In this project, we must code imperatively in the functional programming language OCaml". The joke was well received.
watt 10y ago
Well, isn't this nice - outsourcing the knowledge what makes Sazerac, and how to make it to somebody else, and just declaring that you want it? Would you mind actually making Sazerac in your FP "analogy" as well?
- throwaway7645 10y ago
  Haha...didn't think so many people would respond. There is a Lisp example below. F# is similar, but with pipes and arrows.
- virmundi 10y ago
  I like Clojure, but stopped using it due to not having a good way to define DTOs at a service level (I prefer noisy statically typed languages apparently). Best guess. (-> {} ice (rye :2-fingers) bitters absinthe shake strain garnish) Now I think that strain flipped the returned type from drink to a glass with the drink. All this shows is that OO and FP are duals [1]. I don't claim to get FP perfectly, but my moment of zen was realizing this. 1 - http://wiki.c2.com/?ClosuresAndObjectsAreEquivalent http://wiki.c2.com/?ClosuresAndObjectsAreEquivalent
  - doublerebel 10y ago
    Thank you, I had not seen that c2 page. Many in the JavaScript community have fervent arguments for/against closures/objects (which I do not share). The educated debate in that link is a quality resource on the subject.
  - sankyo 10y ago
    forgot the sugar!
unsoundInput 10y ago
Imperative (especially Java-style OO-imperative) programming will just about always win over non-OO declarative programming in an analogy like that (i.e. a Simulation of a real world process) by nature of them being focused on step-by-step "world manipulation" (and object interaction in case of OO). The value for FP comes from proper abstraction over these processes in functional terms, at which point they can be trivially implemented (few bugs, few iteration cycles to get right). This can probably be done for every problem space, question is at which the abstraction costs outweight the gain. Considering that FP becomes more and more mainstream it's probably more viable than thought in the past, still I imagine system-driven games or complex real-world simulations, with lots of side effects, would lose more from FP than they'd gain.
- vog 10y ago
  > Imperative/OO [...] programming will just about always win over non-OO declarative programming in an analogy like that (i.e. a Simulation of a real world process) Some time ago I thought that, too, but I'm no longer convinced. Directly mutating values (OO style) feels more natural at first, but then you have trouble with side effects and order of execution matters more than it should, you start keeping snapshots of the whole state just to get a consistent world state during computation, otherwise this whole mess produces a whole class of bugs on its own. These problem drive you more and more into FP direction, and the FP style definitely does have its merits in this regard. I think the following article articulates this very well: "A Worst Case for Functional Programming?" http://prog21.dadgum.com/189.html http://prog21.dadgum.com/189.html
imagist 10y ago
First of all, that's not how you make a Sazerac. You rinse the glass with absinthe and toss the absinthe, you don't add it to the mix. There's also an ordering dependence: the rye and bitters can be mixed in either order, but adding ice, shaking, and straining should happen in that order with nothing in between, because the longer the warm ingredients are in contact with the ice, the more you're watering down the drink. I'm not going to go so far as to say the lemon garnish is wrong, but an orange peel rubbed on the rim and then garnished is better IMHO. Second, that's not functional programming, that's calling a library function.
TheCoelacanth 10y ago
I think a better analogy would be: FP => I'll have a Sazerac Imperative => Serve me a Sazerac Imperative programming isn't devoid of abstractions; it just has different ones.

owyn 10y ago

FP is more like: drink(sazerac(garnish(strain(shake(absinthe(bitters(whiskey(ice(glass))))))))) Ultimately it's the same result? The difference is when you can reuse and compose functions.

threeseed 10y ago
Exactly. FP you start with the methods and just keep composing. With OO you start with classes and objects.
- Chyzwar 10y ago
  In OOP you compose nicely as well. It is also easier to understand because it is just conversation. Me(Drinker)->drink( Sazerac(Cocktail) ->garnish() ->strain() ->shake() ->absinthe() ->bitters() ->whiskey() ->ice() ->glass() )
  - sooheon 10y ago
    If you want to create a bar food (Finger Food object, not Cocktail), which also could use a garnish() method, which inherits from which? Or should both objects have a father, Garnishable object to inherit from? It's clear to me that object composition is less flexible than functional composition.
    - kuschku 10y ago
      You just have the method as an aspect that you import into the class ;)
    - Chyzwar 10y ago
      You can have trait/interface. But since garnish will be doing different thing it is OK to have two implementation. FP looks nice in theoretical examples in real world not so much. In FP you will end with garnishFingerFood and garnishCocktail because you need to encode somewhere a specifics of garnish action. In OOP you will have garnish methods on Coctail and FingerFood and specifics and related knowledge how you need to perform garnish will be on object itself. OOP is really powerful concept but failing in languages that have shit implementation. Java, C++ forsake OOP principles for "performance" or are made by people that do not understand concepts (Python, PHP).
      - leshow 10y ago
        From the specific example you're presenting, I don't see how you couldn't just have a Garnishable typeclass, that implements garnish differently for the FingerFood or Cocktail types. The comment that FP isn't nice in the real world is pure baloney. For lots of "real world" IO-bound types of problems there is nothing better suited than a functional programming language with powerful abstractions. Things like monads let you write code in an imperative style without losing any of the benefits of writing in the functional paradigm.
      - dpkp 10y ago
        > In FP you will end with garnishFingerFood and garnishCocktail because you need to encode somewhere a specifics of garnish action. In OOP you will have garnish methods on Coctail and FingerFood and specifics and related knowledge how you need to perform garnish will be on object itself. You're complecting. In the real world of Clojure, you could simply define a protocol and provide different implementations of "garnish".
      - yawaramin 10y ago
        OOP doesn't actually have the market cornered on polymorphism. As my sibling replies show, FP languages have long known how to achieve it.
    - junke 10y ago
      Generic functions: functional yet dynamically dispatched.
      - jeremiep 10y ago
        Generics aren't dynamically dispatched. Java has type erasure and C# emits variants for every instance.
        junke 10y ago
        No, I was talking about (Common) Lisp's generic functions (http://clhs.lisp.se/Body/m_defgen.htm http://clhs.lisp.se/Body/m_defgen.htm). I realize I did not give enough context. Define a generic function: (defgeneric garnish (what with-what)) Specialize it on one or multiple arguments: (defmethod garnish ((c cocktail) (f fruit)) ...) (defmethod garnish ((s sandwich) (h ham)) ...) ... But you can use it like a function: (let ((currified (rcurry #'garnish :curry))) (map 'list currified items))
        jeremiep 10y ago
        Ah my bad! :) These look very much like Clojure's protocols and multi-methods.
        junke 10y ago
        Yes, more like multi-methods, except for standard qualifiers (:around, :before, ...) and user-defined ones. OTOH, Clojure allows you to define a custom dispatch function.
        jeremiep 10y ago
        Ah yes, Clojure has no first-class support for aspects. Its easy enough to monkey patch definitions for the rare case when its needed. Most of the time however I try to avoid aspects as they introduce hidden behaviour in existing functions, which can be hard to reason about at scale, especially with more than a few developers.
  - fnordsensei 10y ago
    I would probably use threading to achieve comparable readability. (def sazerac (-> (mix :ice :whiskey :bitters :absinthe) shake strain garnish)) (drink :me sazerac) I never had a Sazerac. It sounds like a nice drink.
    - greydius 10y ago
      I would create a Cocktail data structure and an instance of Monad for it. sazerac = do add ice add ryeWhisky add bitters add absinthe shake strainInto glass add lemonGarnish main = serve $ makeCocktail sazerac
      - dllthomas 10y ago
        Haskell really is a pretty nice imperative language sometimes.
  - yomly 10y ago
    And people have the cheek to complain about parens in Lisp...
    - jeremiep 10y ago
      Its ironic because foo() and (foo) have the same number of characters; but the later is actually data you can manipulate directly. Reminds me of the blub paradox in beating the averages[1]. [1]: http://paulgraham.com/avg.html http://paulgraham.com/avg.html
    - mahyarm 10y ago
      I once had a comment where I translated a clojure function into it's equivalent syntax in python. It was still pretty hard to read. I think its about how lisp uses function composition for everything makes code hard to parse until you get good at it. Even with the standard practice is to hide it with macros and many small functions. https://news.ycombinator.com/item?id=11174946#11177360 https://news.ycombinator.com/item?id=11174946#11177360
      - bpicolo 10y ago
        I like more forward-building, pipe style FP. Reading outwards on the statement level still makes things hard for me.
  - dustingetz 10y ago
    fluent interfaces from OOP are different than composition because they mutate-and-return the object reference; if the instance is aliased anywhere else in the program there is spooky-action-at-a-distance. Composition is about programming with values without mutation. As far as syntax goes it is a trivial macro to translate `x.f().g()` into `g(f(x))` (clojure actually provides it : http://clojure.org/guides/threading_macros http://clojure.org/guides/threading_macros)
    - yawaramin 10y ago
      > they mutate-and-return.... Not necessarily; you can easily write instance methods which merely copy the existing object.
  - jeremiep 10y ago
    That isn't composition to me but sequencing. Function composition yields a function, not the result of applying the functions. Either you have an object with all of garnish(), strain() and whatnot on it, or each method returns the object to handle the next step in the chain. Either methods don't scale at all without modifying existing code. The real difference is that function composition gives you a reusable function you can further compose while objects keep piling up methods until you're left with god objects or indirection hell.

junke 10y ago

The example is just about abstraction. The imperative equivalent would be: "Give me a Sazerac!" (imperative, hehe)

dllthomas 10y ago
"It is imperative that you give me a Sazerac!"
- junke 10y ago
  Some time ago at University, we had to develop a puzzle solver in FP. In the report's introduction, I wrote something like "In this project, we must code imperatively in the functional programming language OCaml". The joke was well received.

watt 10y ago

Well, isn't this nice - outsourcing the knowledge what makes Sazerac, and how to make it to somebody else, and just declaring that you want it? Would you mind actually making Sazerac in your FP "analogy" as well?

throwaway7645 10y ago
Haha...didn't think so many people would respond. There is a Lisp example below. F# is similar, but with pipes and arrows.
virmundi 10y ago
I like Clojure, but stopped using it due to not having a good way to define DTOs at a service level (I prefer noisy statically typed languages apparently). Best guess. (-> {} ice (rye :2-fingers) bitters absinthe shake strain garnish) Now I think that strain flipped the returned type from drink to a glass with the drink. All this shows is that OO and FP are duals [1]. I don't claim to get FP perfectly, but my moment of zen was realizing this. 1 - http://wiki.c2.com/?ClosuresAndObjectsAreEquivalent http://wiki.c2.com/?ClosuresAndObjectsAreEquivalent
- doublerebel 10y ago
  Thank you, I had not seen that c2 page. Many in the JavaScript community have fervent arguments for/against closures/objects (which I do not share). The educated debate in that link is a quality resource on the subject.
- sankyo 10y ago
  forgot the sugar!

unsoundInput 10y ago

Imperative (especially Java-style OO-imperative) programming will just about always win over non-OO declarative programming in an analogy like that (i.e. a Simulation of a real world process) by nature of them being focused on step-by-step "world manipulation" (and object interaction in case of OO). The value for FP comes from proper abstraction over these processes in functional terms, at which point they can be trivially implemented (few bugs, few iteration cycles to get right). This can probably be done for every problem space, question is at which the abstraction costs outweight the gain. Considering that FP becomes more and more mainstream it's probably more viable than thought in the past, still I imagine system-driven games or complex real-world simulations, with lots of side effects, would lose more from FP than they'd gain.

vog 10y ago
> Imperative/OO [...] programming will just about always win over non-OO declarative programming in an analogy like that (i.e. a Simulation of a real world process) Some time ago I thought that, too, but I'm no longer convinced. Directly mutating values (OO style) feels more natural at first, but then you have trouble with side effects and order of execution matters more than it should, you start keeping snapshots of the whole state just to get a consistent world state during computation, otherwise this whole mess produces a whole class of bugs on its own. These problem drive you more and more into FP direction, and the FP style definitely does have its merits in this regard. I think the following article articulates this very well: "A Worst Case for Functional Programming?" http://prog21.dadgum.com/189.html http://prog21.dadgum.com/189.html

imagist 10y ago

First of all, that's not how you make a Sazerac. You rinse the glass with absinthe and toss the absinthe, you don't add it to the mix. There's also an ordering dependence: the rye and bitters can be mixed in either order, but adding ice, shaking, and straining should happen in that order with nothing in between, because the longer the warm ingredients are in contact with the ice, the more you're watering down the drink. I'm not going to go so far as to say the lemon garnish is wrong, but an orange peel rubbed on the rim and then garnished is better IMHO. Second, that's not functional programming, that's calling a library function.

TheCoelacanth 10y ago

I think a better analogy would be: FP => I'll have a Sazerac Imperative => Serve me a Sazerac Imperative programming isn't devoid of abstractions; it just has different ones.