我最近发现了FP错误(试图学习Haskell),到目前为止,我对我所看到的(一流函数、惰性求值和所有其他好东西)印象深刻。我还不是专家,但我已经开始发现对基本算法进行“功能性”推理比命令式推理更容易(而且我很难回到我必须回到的地方)。

The one area where current FP seems to fall flat, however, is GUI programming. The Haskell approach seems to be to just wrap imperative GUI toolkits (such as GTK+ or wxWidgets) and to use "do" blocks to simulate an imperative style. I haven't used F#, but my understanding is that it does something similar using OOP with .NET classes. Obviously, there's a good reason for this--current GUI programming is all about IO and side effects, so purely functional programming isn't possible with most current frameworks.

My question is, is it possible to have a functional approach to GUI programming? I'm having trouble imagining what this would look like in practice. Does anyone know of any frameworks, experimental or otherwise, that try this sort of thing (or even any frameworks that are designed from the ground up for a functional language)? Or is the solution to just use a hybrid approach, with OOP for the GUI parts and FP for the logic? (I'm just asking out of curiosity--I'd love to think that FP is "the future," but GUI programming seems like a pretty large hole to fill.)


当前回答

所有这些其他答案都建立在函数式编程的基础上,但它们自己做出了很多设计决策。一个基本上完全由函数和简单抽象数据类型构建的库是gloss。下面是它的play函数的源类型

-- | Play a game in a window. Like `simulate`, but you manage your own input events.
play    :: Display              -- ^ Display mode.
        -> Color                -- ^ Background color.
        -> Int                  -- ^ Number of simulation steps to take for each second of real time.
        -> world                -- ^ The initial world.
        -> (world -> Picture)   -- ^ A function to convert the world a picture.
        -> (Event -> world -> world)    
                -- ^ A function to handle input events.
        -> (Float -> world -> world)
                -- ^ A function to step the world one iteration.
                --   It is passed the period of time (in seconds) needing to be advanced.
        -> IO ()

正如您所看到的,它完全通过提供具有简单抽象类型的纯函数来工作,其他库可以帮助您。

其他回答

你可以看看Don Syme在f#上的系列,他演示了如何创建一个gui。下面的链接指向本系列的第三部分(您可以从那里链接到其他两部分)。

使用f#进行WPF开发将是一个非常有趣的GUI范例……

http://channel9.msdn.com/shows/Going+Deep/C9-Lectures-Dr-Don-Syme-Introduction-to-F-3-of-3/

自从第一次提出这个问题以来,函数式响应式编程已经被Elm变得更加主流。

我建议你去http://elm-lang.org上看看,那里也有一些非常优秀的交互式教程,教你如何制作一个功能齐全的浏览器内GUI。

它允许您制作功能齐全的GUI,其中您需要自己提供的代码仅由纯函数组成。我个人认为它比各种Haskell GUI框架更容易上手。

Haskell方法似乎只是包装命令式GUI工具包(如GTK+或wxWidgets),并使用“do”块来模拟命令式样式

这并不是真正的“Haskell方法”——这只是通过命令式接口最直接地绑定到命令式GUI工具包的方法。Haskell恰好有相当突出的绑定。

有几种比较成熟的,或者更具实验性的纯函数式/声明式gui方法,主要是在Haskell中,主要使用函数式响应式编程。

一些例子是:

reflex-platform, https://github.com/reflex-frp/reflex-platform 葡萄柚,http://hackage.haskell.org/package/grapefruit-ui-gtk 无功,http://hackage.haskell.org/package/reactive-glut wxFruit, http://hackage.haskell.org/package/wxFruit reactive-banana, http://hackage.haskell.org/package/reactive-banana

对于那些不熟悉Haskell、Flapjax、http://www.flapjax-lang.org/的人来说,http://www.flapjax-lang.org/是一个基于JavaScript的函数式响应式编程的实现。

所有这些其他答案都建立在函数式编程的基础上,但它们自己做出了很多设计决策。一个基本上完全由函数和简单抽象数据类型构建的库是gloss。下面是它的play函数的源类型

-- | Play a game in a window. Like `simulate`, but you manage your own input events.
play    :: Display              -- ^ Display mode.
        -> Color                -- ^ Background color.
        -> Int                  -- ^ Number of simulation steps to take for each second of real time.
        -> world                -- ^ The initial world.
        -> (world -> Picture)   -- ^ A function to convert the world a picture.
        -> (Event -> world -> world)    
                -- ^ A function to handle input events.
        -> (Float -> world -> world)
                -- ^ A function to step the world one iteration.
                --   It is passed the period of time (in seconds) needing to be advanced.
        -> IO ()

正如您所看到的,它完全通过提供具有简单抽象类型的纯函数来工作,其他库可以帮助您。

函数式编程可能从我上大学的时候就开始了,但我记得函数式编程系统的主要观点是阻止程序员产生任何“副作用”。然而,用户购买软件是由于其产生的副作用,例如更新用户界面。