小编ale*_*ekq的帖子

I've got problem with a Haskell program. I'm trying to change [[Char]] to [[Int]] I've got

["2","2","1","2,2","1"] 

list of char list and I'm trying to change it to [[Int]]

[[2],[2],[1],[2,2],[1]]

I've tried

f :: [String] -> [Int]
f = map read

but it gives me

[2,2,1,*** Exception: Prelude.read: no parse

Can anybody help me with this?

我有 MPI 库的问题。我必须从文件中读取文本并将其发送到另一个进程，例如作为向量。

我编写了以下代码：

#include "mpi.h"
#include <stdio.h>
#include<string.h>
#include<stdlib.h>
#include<string>
#include <fstream>
#include <cstring>
#include <vector>
class PatternAndText
{
public:
    static std::string textPreparaation()
    {
        std::ifstream t("file.txt");
        std::string str((std::istreambuf_iterator<char>(t)), std::istreambuf_iterator<char>());
        std::string text = str;
        return text;
    }

};

int main(int argc, char* argv[])
{
   int size, rank ;
   std::string text;
   std::vector<char> cstr;

    MPI_Init(&argc, &argv);
    MPI_Status status;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    if (rank == 0)
    {
      text = PatternAndText::textPreparaation();
      std::vector<char> cstr(text.c_str(), text.c_str() + text.size() + 1);   
   }

   MPI_Bcast(cstr.data(), cstr.size(), MPI_CHAR,0,MPI_COMM_WORLD);

    if …

我上了一堂简短的课Car：

class Car:

    def __init__(self, brand, model, color, accesories):
        self.brand = brand
        self.model = model
        self.color = color
        self.accesories = ['radio']

    def __str__(self):
        return " accessories {}".format(self.accesories)

    def __iadd__(self, other):
        self.accesories.extend(other)
        print(self.accesories)
        return Car(self.brand, self.model, self.color, self.accesories)

我创建一个对象：

car1 = Car('opel','astra','blue',[])

当我尝试通过以下方式添加其他附件时：

car1 += ['wheel']

它打印：

class Car:

    def __init__(self, brand, model, color, accesories):
        self.brand = brand
        self.model = model
        self.color = color
        self.accesories = ['radio']

    def __str__(self):
        return " accessories {}".format(self.accesories)

    def __iadd__(self, other):
        self.accesories.extend(other)
        print(self.accesories)
        return …

我对haskell功能有问题。我想从列表或列表[[Int]]中删除特定元素

有很多简单的方法可以删除列表[Int]中的元素

例如

removeItem :: Int -> [Int] -> [Int]
removeItem _ []                 = []
removeItem x (y:ys) | x == y    = removeItem x ys
                    | otherwise = y : removeItem x ys

但我不能写

removeItem :: Int -> [[Int]] -> [[Int]]

它应该给出一个结果：

removeItem 1 [[1]，[2,2]，[3]，[1]]

  [[],[2,2],[3],[]]

Run Code Online (Sandbox Code Playgroud)

有谁能够帮助我