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Possibility of duplicate Mongo ObjectId's being generated in two different collections?
...que ID (please let me know if there are more):
Before this discussion, recall that the BSON Object ID consists of:
[4 bytes seconds since epoch, 3 bytes machine hash, 2 bytes process ID, 3 bytes counter]
Here are the three possibilities, so you judge for yourself how likely it is to get a dupe:
...
How to write trycatch in R
...rn value in case of warning
return(NULL)
},
finally={
# NOTE:
# Here goes everything that should be executed at the end,
# regardless of success or error.
# If you want more than one expression to be executed, then you
# need to wr...
Android NDK C++ JNI (no implementation found for native…)
...g the function prototype name wrong, another is failing to load the .so at all. Are you sure that System.loadLibrary() is being called before the method is used?
If you don't have a JNI_OnLoad function defined, you may want to create one and have it spit out a log message just to verify that the l...
Using {} in a case statement. Why?
What is the point with using { and } in a case statement? Normally, no matter how many lines are there in a case statement, all of the lines are executed. Is this just a rule regarding older/newer compilers or there is something behind that?
...
What does gcc's ffast-math actually do?
...tside of IEEE standards, but I can't seem to find information on what is really happening when it's on. Can anyone please explain some of the details and maybe give a clear example of how something would change if the flag was on or off?
...
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...
How to convert a String to its equivalent LINQ Expression Tree?
...nking as a Where clause. If necessary, put it inside a list/array just to call .Where(string) on it! i.e.
var people = new List<Person> { person };
int match = people.Where(filter).Any();
If not, writing a parser (using Expression under the hood) isn't hugely taxing - I wrote one similar (a...
Double not (!!) operator in PHP
...ings or empty arrays) you will get the boolean value FALSE.
It is functionally equivalent to a cast to boolean:
return (bool)$row;
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Objective-C declared @property attributes (nonatomic, copy, strong, weak)
... retaining the copy.
Assign
Assign is somewhat the opposite to copy. When calling the getter of an assign property, it returns a reference to the actual data. Typically you use this attribute when you have a property of primitive type (float, int, BOOL...)
Retain
retain is required when the attribut...
What's the difference between a continuation and a callback?
I've been browsing all over the web in search of enlightenment about continuations, and it's mind boggling how the simplest of explanations can so utterly confound a JavaScript programmer like myself. This is especially true when most articles explain continuations with code in Scheme or use monads....