我一直在挠头试图弄清楚这一点。如何使用foldr1(或任何其他折叠)来获取列表中元组的总和。
\n例子:
\nlist = [(1,2), (3,4)]\nsum = 10\nRun Code Online (Sandbox Code Playgroud)\n我已经尝试过,foldr1 (\\x y -> fst(x) + snd(x) + y) [(1,2),(3,4)]但它不起作用,我怀疑它与执行折叠时创建的类型而不是元组有关。
当我运行上述命令时,我得到以下信息:
\nfoldr1 (\\x y -> fst(x) + snd(x) + y) [(1,2),(3,4)]\n\n\xe2\x80\xa2 Occurs check: cannot construct the infinite type: a ~ (a, a)\n \xe2\x80\xa2 In the second argument of \xe2\x80\x98(+)\xe2\x80\x99, namely \xe2\x80\x98y\xe2\x80\x99\n In the expression: fst (x) + snd (x) + y\n In the first argument of \xe2\x80\x98foldr1\xe2\x80\x99, namely\n \xe2\x80\x98(\\ x y -> fst (x) + …Run Code Online (Sandbox Code Playgroud) 我试图为其中任何一个提供通用方法的打字匹配。在下面的示例中,我有一个预定义的方法识别,它接受通用类型。现在我想定义 OR 类型来识别,它应该接受人或位置。
身份方法来自我无法修改的第三方库。当我尝试下面的场景时,它返回了一个错误
Argument of type '{ city: string; country: string; }' is not assignable to parameter of type 'Person | Location'.
Type '{ city: string; country: string; }' is missing the following properties from type 'Location': ancestorOrigins, hash, host, hostname, and 9 more.
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function identity<Type>(arg: Type): Type {
return arg;
}
interface Person {
name: string;
age: number;
}
interface Location {
city: string;
country: string;
}
identity<Person | Location>({city: 'SA', country: 'USA'})
Run Code Online (Sandbox Code Playgroud) 类型类Data. Bits有一个方法,如果参数的类型是有符号类型,isSigned :: a -> Bool则返回该方法。True文档明确指出该参数被忽略。类型类中还有其他类似的方法;还有其他类型类也具有此类方法。我的问题:为什么选择这样的设计?该值仅取决于类型,所以为什么不只是:
isSigned :: Bool
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作为后续:假设我有一个带有 nullary method 的自定义类型类method :: Bool。是否有任何理由改变它并这样做Data.Bits,即method :: a -> Bool?
我只是 Debian 12 用户一周,说实话,这已经是我第三次尝试正确安装了。今天我尝试配置我的 WiFi 适配器 TP-Link Archer T4U Plus AC1300,并在其上安装驱动程序。首先,我遵循了以下说明:https://github.com/morrownr/88x2bu-20210702,它实际上对我有所帮助,而之前安装的 Debian 这次一切都出了问题。
因此,在努力解决问题的同时,我找到了这个存储库https://github.com/fastoe/RTL8812BU。完成后,sudo apt update && sudo apt upgrade我注意到有趣的新 6.1.0-18 内核模块,它与我88x2bu和nvidia-current/525.147.05驱动程序发生 cpnflicting。我试图在复制的存储库文件夹中使用remove-driver.sh卸载第一个,但问题仍然出现。这是执行任何sudo apt installor操作时的输出sudo apt upgrade:
Setting up linux-image-6.1.0-18-amd64 (6.1.76-1) ...
I: /initrd.img is now a symlink to boot/initrd.img-6.1.0-18-amd64
/etc/kernel/postinst.d/dkms:
dkms: running auto installation service for kernel 6.1.0-18-amd64.
Sign command: /usr/lib/linux-kbuild-6.1/scripts/sign-file
Signing key: /var/lib/dkms/mok.key
Public certificate (MOK): /var/lib/dkms/mok.pub
Building module:
Cleaning build area...
'make' all …Run Code Online (Sandbox Code Playgroud) 我有一个我接受的非阻塞连接套接字:
我有一个非阻塞套接字连接,在收到数据包后,我尝试使用 recv 读取更多数据。
struct sockaddr accepted_address;
socklen_t accepted_address_size = sizeof(accepted_address);
int fd = accept(server_fd, &accepted_address, &accepted_address_size);
make_nonblocking(fd);
... // wait when socket is ready to give me data
char buffer[BUF_SIZE];
int used = 0;
while (true) {
int bytes_received = recv(fd, buffer, BUF_SIZE, 0);
if (bytes_received > 0) { /* OK */ }
else if (bytes_received < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK) {
/* Should wait for more data, BUT I WILL WAIT INDEFINITELY!!! …Run Code Online (Sandbox Code Playgroud) boost::atomic 要求 T 可以轻松复制。但为什么下面的代码有效呢boost::atomic<atom>?
#include <chrono>
#include <iostream>
#include <memory>
#include <unordered_set>
#include <parallel/algorithm>
#include <boost/algorithm/cxx11/all_of.hpp>
#include <boost/atomic.hpp>
#include <boost/optional/optional.hpp>
#include <boost/range/algorithm/copy.hpp>
#include <boost/range/algorithm/count_if.hpp>
#include <boost/range/algorithm/remove_if.hpp>
#include <boost/range/algorithm/sort.hpp>
#include <boost/range/algorithm/unique.hpp>
#include <boost/range/irange.hpp>
#include <boost/range/numeric.hpp>
typedef uint32_t vint; // Integer for vertex IDs
constexpr vint vmax = std::numeric_limits<vint>::max(); // Used as invalid ID
struct atom {
boost::atomic<float> str; // Total weighted degree of the community members
boost::atomic<vint> child; // Last vertex that is merged to this vertex
std::string c; …Run Code Online (Sandbox Code Playgroud) std::from_chars将位字符串 (base=2) 解析为有符号 8 位整数时失败,并出现一般错误,而std::stoi解析有符号 8 位整数时不会出现错误。
下面程序中的两个块都解析相同的位串。程序以调用std::abort第二个块中的第一个断言结束。std::stoi解析相同的位串没有错误。
// Compile: g++ -std=c++17 -O0 -g main.cc -o main
#include <string>
#include <cassert>
#include <charconv>
#include <cstdint>
int main()
{
{
std::string bits = "10011100";
int base = 2;
std::int8_t num = std::stoi(bits.c_str(), nullptr, base);
assert(num == -100);
}
{
// Bug found in std::from_chars when type is int8_t and base=2.
std::string bits = "10011100";
int base = 2;
std::int8_t num;
auto [ptr, ec] = …Run Code Online (Sandbox Code Playgroud) 我得到了这个函数,我添加了这段代码来遍历数组中的数字,然后我有另一个变量来计算奇数的数量,放入第二个数组
int CopySelected(const int array[], int size, int odd_numbers[])
{
int oddCounter = 0;
int i;
for (i = 0; i < size; ++i)
{
if (array[i]%2 != 0)
odd_numbers[++oddCounter] = array[i];
}
return oddCounter;
}
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该代码因错误而通过,但失败了。有什么建议么?
当我尝试创建主题时会发生这种情况
TypeError: this.auth.getUniverseDomain is not a function
at GrpcClient.createStub (/Users/<...>/node_modules/google-gax/src/grpc.ts:418:48)
at processTicksAndRejections (node:internal/process/task_queues:95:5)
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示例代码:
pubSubClient = new PubSub({
"projectId": "project_name"
});
initTopic = async () => {
// Creates a new topic if it does not exist
const [topics] = await this.pubSubClient.getTopics()
RootLogger.info("topic names: " + topics.join(","))
const topicExists = topics.some(topic => topic.name.endsWith(this.topicName));
if (topicExists) {
RootLogger.info(`Topic ${this.topicName} already exists.`);
} else {
await this.pubSubClient.createTopic(this.topicName);
RootLogger.info(`Topic ${this.topicName} created.`);
}
}
Run Code Online (Sandbox Code Playgroud) authentication node.js typescript google-cloud-platform google-cloud-pubsub