Question

有没有办法将这些功能组合在一起？

data Patient = Patient
  { name :: Name,
    sex :: Sex,
    age :: Int,
    height :: Int,
    weight :: Int,
    bloodType :: BloodType
  }

canDonate :: BloodType -> BloodType -> Bool

canDonateTo :: Patient -> Patient -> Bool

目前我只是手动应用它们

canDonateTo :: Patient -> Patient -> Bool
canDonateTo x y = canDonate (bloodType x) (bloodType y)

但是，我想知道是否有更好的方法来做到这一点。

Answer 1

使用Data.Function.on：

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Test {
  public static void main(String[] args) throws Exception {
    // these commands work
    run("/bin/sh", "-c", "echo $PATH");
    run("/bin/bash", "-c", "echo $PATH");
    run("/bin/zsh", "-c", "echo $PATH");

    // these commands all work when I run them manually in a terminal
    // but fail here with "zsh:1: command not found: ..."
    run("/bin/zsh", "-c", "node -v");
    run("/bin/zsh", "-c", "npm -v");
  }

  private static void run(String... command) throws Exception {
    ProcessBuilder processBuilder = new ProcessBuilder();
    processBuilder.redirectErrorStream(true);
    processBuilder.command(command);
    Process process = processBuilder.start();
    try(BufferedReader br = new BufferedReader(new InputStreamReader(process.getInputStream()))) {
      for(String line = br.readLine(); line != null; line = br.readLine()) {
        System.out.println(line);
      }
    }
    System.out.println("return value: " + process.waitFor());
  }
}

（基本上，您的方法只是内联了 /usr/bin:/bin:/usr/sbin:/sbin return value: 0 /usr/bin:/bin:/usr/sbin:/sbin return value: 0 /usr/bin:/bin:/usr/sbin:/sbin return value: 0 zsh:1: command not found: node return value: 127 zsh:1: command not found: npm return value: 127 的定义，可以将其定义为

@types/react-color@2.17.5

)

如何组合一起返回 Bool 的函数

1 个答案: