大约有 16,000 项符合查询结果（耗时：0.0297秒） [XML]
Hidden Features of Java
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Double Brace Initialization took me by surprise a few months ago when I first discovered it, never heard of it before.
ThreadLocals are typically not so widely known as a way to store per-thread state.
Since JDK 1.5 Java has h...
Applying a function to every row of a table using dplyr?
... of dplyr 0.2 (I think) rowwise() is implemented, so the answer to this problem becomes:
iris %>%
rowwise() %>%
mutate(Max.Len= max(Sepal.Length,Petal.Length))
Non rowwise alternative
Five years (!) later this answer still gets a lot of traffic. Since it was given, rowwise is increas...
Does a javascript if statement with multiple conditions test all of them?
...nditions to test for, does javascript test them all regardless, or will it bail before testing them all if it's already false?
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How to suppress GCC warnings from library headers?
I have a project that uses log4cxx, boost, etc. libraries whose headers generate lots of (repetitive) warnings. Is there a way to suppress warnings from library includes (i.e. #include ) or includes from certain paths? I'd like to use -Wall and/or -Wextra as usual on project code without relevant in...
Why is this F# code so slow?
...tation in C# and F#. The C# version is 10 times faster for two strings of about 1500 chars. C#: 69 ms, F# 867 ms. Why? As far as I can tell, they do the exact same thing? Doesn't matter if it is a Release or a Debug build.
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Is git's semi-secret empty tree object reliable, and why is there not a symbolic name for it?
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This thread mentions:
If you don't remember the empty tree sha1, you can always derive it with:
git hash-object -t tree /dev/null
Or, as Ciro Santilli proposes in the comments:
printf '' | git hash-object --stdin -t tree
Or, as seen here, from Colin Schimmel...
Filtering collections in C#
I am looking for a very fast way to filter down a collection in C#. I am currently using generic List collections, but am open to using other structures if they perform better.
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ant warning: “'includeantruntime' was not set”
I receive the following warning:
7 Answers
7
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What is a Python equivalent of PHP's var_dump()? [duplicate]
When debugging in PHP, I frequently find it useful to simply stick a var_dump() in my code to show me what a variable is, what its value is, and the same for anything that it contains.
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Why doesn't the example compile, aka how does (co-, contra-, and in-) variance work?
...iant type parameter is one which is allowed to vary down as the class is subtyped (alternatively, vary with subtyping, hence the "co-" prefix). More concretely:
trait List[+A]
List[Int] is a subtype of List[AnyVal] because Int is a subtype of AnyVal. This means that you may provide an instance ...