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r - Understanding exactly when a data.table is a reference to (vs a copy of) another data.table

I'm having a little trouble understanding the pass-by-reference properties of data.table. Some operations seem to ... if someone could explain this to me. Question&Answers:os...

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

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368 views

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javascript - Capture HTML Canvas as gif/jpg/png/pdf?

Is it possible to capture or print what's displayed in an html canvas as an image or pdf? I'd like to ... and be able to generate a png from that image. Question&Answers:os...

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

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146 views

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What does <![CDATA[]]> in XML mean?

I often find this strange CDATA tag in XML files: <![CDATA[some stuff]]> I have observed that this CDATA tag ... I write in XML tags some sort of data? Question&Answers:os...

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

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c# - How to Sort a List<T> by a property in the object

I have a class called Order which has properties such as OrderId, OrderDate, Quantity, and Total. I have a list of this ... order id. How can i do this in C#? Question&Answers:os...

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

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c - Pointer Arithmetic

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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How to filter a Java Collection (based on predicate)?

I want to filter a java.util.Collection based on a predicate. Question&Answers:os...

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

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What's the difference between "STL" and "C++ Standard Library"?

Someone brought this article to my attention that claims (I'm paraphrasing) the STL term is misused to refer to ... term STL? Or is this an isolated opinion? Question&Answers:os...

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

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.net - C# difference between == and Equals()

I have a condition in a silverlight application that compares 2 strings, for some reason when I use == it returns ... } Any reason as to why this is happening? Question&Answers:os...

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

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python - How do I watch a file for changes?

I have a log file being written by another process which I want to watch for changes. Each time a change occurs I' ... the file the way it does on a local disk. Question&Answers:os...

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

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html - How to load up CSS files using Javascript?

Is it possible to import css stylesheets into a html page using Javascript? If so, how can it be done? P.S ... the javascript file will be hosted on my server). Question&Answers:os...

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

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249 views

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javascript - How to deep merge instead of shallow merge?

Both Object.assign and Object spread only do a shallow merge. An example of the problem: // No object nesting const x ... .assign(). Is there a 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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Android:java.lang.OutOfMemoryError: Failed to allocate a 23970828 byte allocation with 2097152 free bytes and 2MB until OOM

I want to show the Bitmap image in ImageView from sd card which is stored already. After run my ... android.internal.os.ZygoteInit.main(ZygoteInit.java:698) Question&Answers:os...

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

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246 views

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javascript - What is destructuring assignment and its uses?

I have been reading about Destructuring assignment introduced in ES6. What is the purpose of this syntax, why was it ... of how it might be used in practice? Question&Answers:os...

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

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C++ Returning reference to local variable

Is the following code (func1()) correct if it has to return i? I remember reading somewhere that there is a problem when ... = new int; *p = 1; return p; } Question&Answers:os...

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

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sql - NOT IN vs NOT EXISTS

Which of these queries is the faster? NOT EXISTS: SELECT ProductID, ProductName FROM Northwind..Products p WHERE NOT ... I think I'll stick with NOT EXISTS. Question&Answers:os...

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

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227 views

1 answer

css float - What does the CSS rule "clear: both" do?

What does the following CSS rule do: .clear { clear: both; } And why do we need to use it? Question&Answers:os...

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

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514 views

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javascript - Pass correct "this" context to setTimeout callback?

How do I pass context into setTimeout? I want to call this.tip.destroy() if this.options.destroyOnHide after 1000 ... try the above, this refers to the window. Question&Answers:os...

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

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262 views

1 answer

node.js - How to fix npm throwing error without sudo

I just installed node and npm through the package on nodejs.org, and whenever I try to search or install something with ... npm-debug.log npm ERR! not ok code 0 Question&Answers:os...

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

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248 views

1 answer

Should I use the datetime or timestamp data type in MySQL?

Would you recommend using a datetime or a timestamp field, and why (using MySQL)? I'm working with PHP on the server side. Question&Answers:os...

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

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How to get a list of installed android applications and pick one to run

I asked a similar question to this earlier this week but I'm still not understanding how to get a list of all ... do I use this to run a specific application? Question&Answers:os...

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

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179 views

1 answer

Are global variables in PHP considered bad practice? If so, why?

function foo () { global $var; // rest of code } In my small PHP projects I usually go the procedural way. I ... , I do global $var;. Is this bad practice? Question&Answers:os...

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

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130 views

1 answer

r - Calculate group mean (or other summary stats) and assign to original data

I want to calculate mean (or any other summary statistics of length one, e.g. min, max, length, sum) of a numeric variable ... a 20 15 3 b 100 150 4 b 200 150 Question&Answers:os...

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

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305 views

1 answer

Difference between static class and singleton pattern?

What real (i.e. practical) difference exists between a static class and a singleton pattern? Both can be ... thread-safe. Is there any other difference? 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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error handling - Does a finally block always get executed in Java?

Considering this code, can I be absolutely sure that the finally block always executes, no matter what something() is? ... if this will get printed out"); } Question&Answers:os...

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

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258 views

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c++ - When to use volatile with multi threading?

If there are two threads accessing a global variable then many tutorials say make the variable volatile to prevent ... of volatile in a multi-threaded program? Question&Answers:os...

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

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225 views

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python - Passing HTML to template using Flask/Jinja2

I'm building an admin for Flask and SQLAlchemy, and I want to pass the HTML for the different inputs to ... I disable that so that the HTML renders correctly? Question&Answers:os...

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

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298 views

1 answer

rust - Return local String as a slice (&str)

There are several questions that seem to be about the same problem I'm having. For example see here and here. Basically ... .push_str("ACTG"); } &string[..] } Question&Answers:os...

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

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211 views

1 answer

.net - What is the purpose of "return await" in C#?

Is there any scenario where writing method like this: public async Task<SomeResult> DoSomethingAsync() { / ... additional overhead of additional await layer? Question&Answers:os...

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

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