小编zer*_*ing的帖子

我想像这样计算binom:

let t = seq { 1..10 } |> Seq.takeWhile (fun e -> e % 2 == 0)

但编译器抱怨

playground.fsx(27,59): error FS0001: The type 'int' does not support the operator '=='

我究竟做错了什么？

如何设计具有角度材质布局的布局,如:

我从材料设计中得到了一个例子

描述:一个md-content框,阴影悬停在md工具栏上.

我正在为程序员阅读分类理论,我无法弄清楚究竟是什么类别.

我们考虑一下这种Bool类型.是Bool一个类别和/ True或False对象(居民)？

我正在尝试安装

stack install ghc-mod

我有以下错误:

In the dependencies for ghc-mod-5.8.0.0:
    Cabal-2.0.1.1 from stack configuration does not match >=1.18 && <1.25 (latest matching version is 1.24.2.0)
    base-4.10.1.0 from stack configuration does not match >=4.6.0.1 && <4.10 (latest matching version is 4.9.1.0)
    cabal-helper must match <0.8 && >=0.7.3.0, but the stack configuration has no specified version (latest matching version is 0.7.3.0)
    extra-1.6.2 from stack configuration does not match <1.6 && >=1.4 (latest matching version is 1.5.3)
    ghc-8.2.2 from stack configuration does not …

我有以下代码,没有编译:

import React from 'react';
import { AppBar, Toolbar } from 'material-ui';
import { Typography } from 'material-ui';
import { MuiThemeProvider, createMuiTheme } from 'material-ui/styles';
import {cyan, red} from 'material-ui/colors';
import { red400 } from 'material-ui/styles/colors';


const theme = createMuiTheme({
  palette: {
    primary: red400,
    secondary: cyan, 
  },
});

const View = (props) => (
  <MuiThemeProvider theme={theme}>
    <AppBar position="static">
      <Toolbar>
      <Typography variant="title">
        {props.title}
      </Typography>          
      </Toolbar>
    </AppBar>
  </MuiThemeProvider>
);
export default View;

它说:

Failed to compile
./src/Dashboard/AppBar/Views/View.js
Module not found: Can't resolve …

我有以下来自互联网的代码片段：

calculateLength :: LengthMonad Int
calculateLength = do
  -- all the IO operations have to be lifted to the IO monad in the monad stack
  liftIO $ putStrLn "Please enter a non-empty string: "
  s <- liftIO getLine
  if null s
    then throwError "The string was empty!"
    else return $ length s

并不能理解，为什么作者使用liftIO？

的目的是liftIO什么？

它的定义如下：

class (Monad m) => MonadIO m where
    -- | Lift a computation from the 'IO' monad.
    liftIO :: IO a -> …

我写了一个设置cookie并删除它的Web应用程序.为了澄清方案,我的意思是看下面的代码片段.

package main

import (
    "fmt"
    "github.com/gorilla/mux"
    "net/http"
    "time"
)

func rootHandler(rw http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(rw, "Hello Foo")

}

func setCookieHandler(rw http.ResponseWriter, r *http.Request) {
    c := &http.Cookie{
        Name:     "storage",
        Value:    "value",
        Path:     "/",
        MaxAge:   0,
        HttpOnly: true,
    }

    http.SetCookie(rw, c)
}

func deleteCookieHandler(rw http.ResponseWriter, r *http.Request) {

    c, err := r.Cookie("storage")
    if err != nil {
        panic(err.Error())
    }
    c.Name = "Deleted"
    c.Value = "Unuse"
    c.Expires = time.Unix(1414414788, 1414414788000)
}

func readCookieHandler(rw http.ResponseWriter, r *http.Request) {

    c, err := …

我试图在编程环境中理解同构和同态,需要一些帮助.

在FPiS一书中,它解释了:

让我们从同态开始:

"foo".length + "bar".length == ("foo" + "bar").length

这里,长度是String to Int保留幺半群结构的函数.

• 为什么这是一个同态？

• 为什么它保留了幺半群结构？

• 例如map在list函数上是同态吗？

关于同构,我从一本书中得到了以下解释:

M和N之间的幺半群同构具有两个同态f和g,其中f和T g以及g和T f都是同一性函数.例如,串联的String和List [Char] monoid是同构的.两个布尔幺半群(假,||)和(真,&&)也是同构的,通过!(否定)功能.

为什么(false, ||), (true, &&)和String and List[Char] monoids with concatenation同构？

我正在使用Webpack 4并安装" font-awesome": "^4.7.0"in package.json.然后我尝试将其导入到我的内容中index.scss,如下所示:

@import '~font-awesome/scss/font-awesome.scss';
@import '~bootstrap/scss/bootstrap.scss';  

我有以下错误消息:

ERROR in ./src/index.scss (./node_modules/css-loader!./node_modules/sass-loader/lib/loader.js!./src/index.scss)
    Module not found: Error: Can't resolve '../fonts/fontawesome-webfont.eot' in '/Volumes/Develop/react-reason/cockpit/src'
     @ ./node_modules/css-loader!./node_modules/sass-loader/lib/loader.js!./src/index.scss 7:414-457

    ERROR in ./src/index.scss (./node_modules/css-loader!./node_modules/sass-loader/lib/loader.js!./src/index.scss)
    Module not found: Error: Can't resolve '../fonts/fontawesome-webfont.eot?v=4.7.0' in '/Volumes/Develop/react-reason/cockpit/src'
     @ ./node_modules/css-loader!./node_modules/sass-loader/lib/loader.js!./src/index.scss 7:332-383

    ERROR in ./src/index.scss (./node_modules/css-loader!./node_modules/sass-loader/lib/loader.js!./src/index.scss)
    Module not found: Error: Can't resolve '../fonts/fontawesome-webfont.svg?v=4.7.0' in '/Volumes/Develop/react-reason/cockpit/src'
     @ ./node_modules/css-loader!./node_modules/sass-loader/lib/loader.js!./src/index.scss 7:806-857

    ERROR in ./src/index.scss (./node_modules/css-loader!./node_modules/sass-loader/lib/loader.js!./src/index.scss)
    Module not found: Error: Can't resolve '../fonts/fontawesome-webfont.ttf?v=4.7.0' in '/Volumes/Develop/react-reason/cockpit/src'
     @ ./node_modules/css-loader!./node_modules/sass-loader/lib/loader.js!./src/index.scss 7:711-762

    ERROR in …

我正在尝试使用https://www.testcontainers.org/固有的https://github.com/testcontainers/testcontainers-scala，如下所示：

final class MessageSpec extends BddSpec
  with ForAllTestContainer
  with BeforeAndAfterAll {


  override val container = GenericContainer("sweetsoft/sapmock").configure{ c =>
    c.addExposedPort(8080)
    c.withNetwork(Network.newNetwork())
  }

  override def beforeAll() {
  }


  feature("Process incoming messages") {  

当我使用命令运行测试时sbt test，出现以下异常：

15:22:23.171 [pool-7-thread-2] ERROR  [sweetsoft/sapmock:latest] - Could not start container
org.testcontainers.containers.ContainerLaunchException: Timed out waiting for container port to open (localhost ports: [32775] should be listening)
        at org.testcontainers.containers.wait.strategy.HostPortWaitStrategy.waitUntilReady(HostPortWaitStrategy.java:47)
        at org.testcontainers.containers.wait.strategy.AbstractWaitStrategy.waitUntilReady(AbstractWaitStrategy.java:35)
        at org.testcontainers.containers.wait.HostPortWaitStrategy.waitUntilReady(HostPortWaitStrategy.java:23)
        at org.testcontainers.containers.wait.strategy.AbstractWaitStrategy.waitUntilReady(AbstractWaitStrategy.java:35)
        at org.testcontainers.containers.GenericContainer.waitUntilContainerStarted(GenericContainer.java:582)

该图像是本地图像：

docker images
REPOSITORY                    TAG                 IMAGE ID            CREATED …