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mongodb group values by multiple fields
... $slice just off the basic aggregation result. For "large" results, run parallel queries instead for each grouping ( a demonstration listing is at the end of the answer ), or wait for SERVER-9377 to resolve, which would allow a "limit" to the number of items to $push to an array.
db.books.aggregate(...
Flask vs webapp2 for Google App Engine
...easily avoid it. Moreover, despite the fact I sympathize with Flask, I'm really impressed with webapp2 and have my hands itching to try it out. Thank you for answer and for webapp2!
– Anton Moiseev
Jul 22 '11 at 9:52
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What's the difference between __PRETTY_FUNCTION__, __FUNCTION__, __func__?
... = "function-name";
appeared, where function-name is the name of the lexically-enclosing function. This name is the unadorned name of the function.
Note that it is not a macro and it has no special meaning during preprocessing.
__func__ was added to C++ in C++11, where it is specified as containi...
Watermark / hint text / placeholder TextBox
How can I put some text into a TextBox which is removed automatically when user types something in it?
33 Answers
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Android: install .apk programmatically [duplicate]
...ade this with help from
Android download binary file problems
and Install Application programmatically on Android .
5 ...
How does RegexOptions.Compiled work?
...methods on the Regex class.
For example: Regex.Replace, Regex.Match etc.. all use the Regex cache.
The size of the cache can be increased by setting Regex.CacheSize. It accepts changes in size any time during your application's life cycle.
New regular expressions are only cached by the static hel...
When do I use a dot, arrow, or double colon to refer to members of a class in C++?
...d for three different scenarios that are always well-defined. Knowing this allows you to immediately know quite a lot about a and b just by looking at a::b, a.b, or a->b, respectively, in any code you look at.
a::b is only used if b is a member of the class (or namespace) a. That is, in this c...
What is the performance cost of having a virtual method in a C++ class?
...3ghz in-order PowerPC processor. On that architecture, a virtual function call costs 7 nanoseconds longer than a direct (non-virtual) function call.
So, not really worth worrying about the cost unless the function is something like a trivial Get()/Set() accessor, in which anything other than inli...
stringstream, string, and char* conversion confusion
...the temporary string const, because any changes to it might cause it to re-allocate and thus render cstr invalid. It is therefor safer to not to store the result of the call to str() at all and use cstr only until the end of the full expression:
use_c_str( stringstream.str().c_str() );
Of course,...
Why do == comparisons with Integer.valueOf(String) give different results for 127 and 128?
...s a sizable difference - one is considered an object, which means you can call methods and interact with it in abstract data structures, like List. The other is a primitive, which is just a raw value.
– Makoto
Jan 2 '14 at 6:07
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