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c++ - Why can't variables be declared in a switch statement?

I've always wondered this - why can't you declare variables after a case label in a switch statement? In C+ ... other languages too. Why is this such a problem? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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265 views

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macos - Setting environment variables on OS X

What is the proper way to modify environment variables like PATH in OS X? I've looked on Google a little bit and found ... ? I'm running OS X v10.5 (Leopard). Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - What is a Future and how do I use it?

I get the following error: A value of type 'Future<int>' can't be assigned to a variable of type 'int' It might be ... my value when all I have is a Future<T>? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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python - How to copy a dictionary and only edit the copy

Can someone please explain this to me? This doesn't make any sense to me. I copy a dictionary into another and edit the ... 'key2': 'WHY?!', 'key1': 'value1'} Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c# - Fastest Way of Inserting in Entity Framework

I'm looking for the fastest way of inserting into Entity Framework. I'm asking this because of the scenario ... and this will lead to an incomplete transaction. Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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git - Checkout another branch when there are uncommitted changes on the current branch

Most of the time when I try to checkout another existing branch, Git doesn't allow me if I have some uncommitted ... That is, is it helpful in some situations? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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r - How to add leading zeros?

I have a set of data which looks something like this: anim <- c(25499,25500,25501,25502,25503,25504) sex <- c ... add two or three zeros before the animal id's? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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Why does a GraphQL query return null?

I have an graphql/apollo-server/graphql-yoga endpoint. This endpoint exposes data returned from a database (or a ... Why is GraphQL not returning the data? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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Convert date to another timezone in JavaScript

I am looking for a function to convert date in one timezone to another. It need two parameters, date (in format "2012 ... .tab Is there an easy way to do this? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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How do you use the ? : (conditional) operator in JavaScript?

In simple words, what is the ?: (conditional, "ternary") operator and how can I use it? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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android - Fling gesture detection on grid layout

I want to get fling gesture detection working in my Android application. What I have is a GridLayout that contains ... far and I was hoping for some pointers. Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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floating point - What is the best way to compare floats for almost-equality in Python?

It's well known that comparing floats for equality is a little fiddly due to rounding and precision issues. ... a standard library function for this somewhere? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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javascript - setTimeout or setInterval?

As far as I can tell, these two pieces of javascript behave the same way: Option A: function ... there any difference between using setTimeout and setInterval? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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html - Best way to center a <div> on a page vertically and horizontally?

This question already has answers here: Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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php - How to configure XAMPP to send mail from localhost?

I am trying to send mail from localhost. but i am unable to send the mail from localhost so can anybody ... to reconfigure my xampp to send mail from localhost Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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226 views

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jquery - Difference between .on('click') vs .click()

Is there any difference between the following code? $('#whatever').on('click', function() { /* your code here */ }); ... (function() { /* your code here */ }); Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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192 views

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Accessing the web page's HTTP Headers in JavaScript

How do I access a page's HTTP response headers via JavaScript? Related to this question, which was modified ... the HTTP request header fields via JavaScript? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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187 views

1 answer

math - Why can't decimal numbers be represented exactly in binary?

There have been several questions posted to SO about floating-point representation. For example, the decimal number 0.1 ... to the left and to the right. Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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188 views

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sql - How to create id with AUTO_INCREMENT on Oracle?

It appears that there is no concept of AUTO_INCREMENT in Oracle, up until and including version 11g. How can ... that behaves like auto increment in Oracle 11g? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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353 views

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python - Get statistics for each group (such as count, mean, etc) using pandas GroupBy?

I have a data frame df and I use several columns from it to groupby: df['col1','col2','col3','col4']. ... How do I get group-wise statistics for a dataframe? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.5k views

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io - A non-blocking read on a subprocess.PIPE in Python

I'm using the subprocess module to start a subprocess and connect to its output stream (standard output). ... subprocess.PIPE) output_str = p.stdout.readline() Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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57 views

1 answer

javascript - Is there an "exists" function for jQuery?

How can I check the existence of an element in jQuery? The current code that I have is this: if ($( ... to approach this? Perhaps a plugin or a function? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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253 views

1 answer

language agnostic - What is a magic number, and why is it bad?

Closed. This question is opinion-based. It is not currently accepting answers. Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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82 views

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javascript - How do I create and read a value from cookie?

How can I create and read a value from a cookie in JavaScript? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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402 views

1 answer

css - What is the difference between visibility:hidden and display:none?

The CSS rules visibility:hidden and display:none both result in the element not being visible. Are these synonyms? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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405 views

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datetime - How do I get current date/time on the Windows command line in a suitable format for usage in a file/folder name?

Update: Now that it's 2016 I'd use PowerShell for this unless there's a really compelling backwards-compatible ... are some that will do nice date formatting). Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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68 views

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php - How Can I add HTML And CSS Into PDF

Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers. Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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67 views

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ios - How do I create delegates in Objective-C?

I know how delegates work, and I know how I can use them. But how do I create them? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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