大约有 32,000 项符合查询结果（耗时：0.0405秒） [XML]
Pass a data.frame column name to a function
...l_name,col1,col2){
df$col_name <- df$col1 + df$col2
df
}
#Call foo() like this:
foo(dat,z,x,y)
The problem here is that df$col1 doesn't evaluate the expression col1. It simply looks for a column in df literally called col1. This behavior is described in ?Extract under the secti...
What's the difference between using “let” and “var”?
...does not create a property on the global object:
var foo = "Foo"; // globally scoped
let bar = "Bar"; // globally scoped
console.log(window.foo); // Foo
console.log(window.bar); // undefined
Redeclaration
In strict mode, var will let you re-declare the same variable in the same scope while let...
What should I use Android AccountManager for?
.../ Alarm
only available from API >= 7 (this doesn't matter anymore)
Finally, if you use a SyncAdapter, seriously consider Firebase Cloud Messaging (previously Google Cloud Messaging) aka "push notifications" to have fresher updates and optimized battery usage.
...
In HTML5, should the main navigation be inside or outside the element?
...element is for navigation around that site only. I was just being clear is all.
– Ian Devlin
Feb 2 '11 at 16:54
@Matth...
How to create an object for a Django model with a many to many field?
...
For future visitors, you can create an object and all of its m2m objects in 2 queries using the new bulk_create in django 1.4. Note that this is only usable if you don't require any pre or post-processing on the data with save() methods or signals. What you insert is exactly...
What does the thread_local mean in C++11?
...al variables in a function. The global/static variables can be accessed by all the threads (possibly synchronized access using locks). And the thread_local variables are visible to all the threads but can only modified by the thread for which they are defined? Is it correct?
...
Natural Sort Order in C#
...
@linquize - He said .NET not Mono, so Linux/OSX isn't really a concern. Windows Phone/Metro didn't exist in 2008 when this answer was posted. And how often do you do file operations in Silverlight? So for the OP, and probably most other people, it was a suitable answer. In any cas...
Encrypting & Decrypting a String in C# [duplicate]
...be getting a lot of upvotes, I've updated it to fix silly bugs and to generally improve the code based upon comments and feedback. See the end of the post for a list of specific improvements.
As other people have said, Cryptography is not simple so it's best to avoid "rolling your own" encryption ...
Coding Practices which enable the compiler/optimizer to make a faster program
...act.
Expect to be disappointed and to have to work very hard indeed for small performance improvements. Modern compilers for mature languages such as Fortran and C are very, very good. If you read an account of a 'trick' to get better performance out of code, bear in mind that the compiler writer...
Should I compile release builds with debug info as “full” or “pdb-only”?
...t there is some impact on the speed and size of JIT optimized code and a small impact on code quality with /debug:full. We recommend /debug:pdbonly or no PDB for generating release code.
– Allon Guralnek
Feb 16 '12 at 9:18
...