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What is the use of hashCode in Java?
...e), then it uses the equals() method to evaluate if the objects are equal, and then decide if contains() is true or false, or decide if element could be added in the set or not.
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Assign multiple columns using := in data.table, by group
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Thanks for this answer and the examples. How should I modify the following line in order to get two columns for each objectName from the dim output, rather than one column with two rows? data.table(objectName=ls())[,c("rows","cols"):=dim(get(objec...
C++ Double Address Operator? (&&)
I'm reading STL source code and I have no idea what && address operator is supposed to do. Here is a code example from stl_vector.h :
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is of a type that is invalid for use as a key column in an index
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A unique constraint can't be over 8000 bytes per row and will only use the first 900 bytes even then so the safest maximum size for your keys would be:
create table [misc_info]
(
[id] INTEGER PRIMARY KEY IDENTITY NOT NULL,
[key] nvarchar(450) UNIQUE NOT NULL,
[v...
How to display a list inline using Twitter's Bootstrap
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According to Bootstrap documentation of 2.3.2 and 3, the class should be defined like this:
Bootstrap 2.3.2
<ul class="inline">
<li>...</li>
</ul>
Bootstrap 3
<ul class="list-inline">
<li>...</li>
</ul>
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Is null an Object?
...case - any method invocation on a null results in a NullPointerException.
And this is what the Java Language Specification has to say on this topic:
There is also a special null type, the
type of the expression null, which has
no name. Because the null type has no
name, it is impossible t...
How can I put a database under git (version control)?
I'm doing a web app, and I need to make a branch for some major changes, the thing is, these changes require changes to the database schema, so I'd like to put the entire database under git as well.
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Check for installed packages before running install.packages() [duplicate]
... computers. One of its lines contains the install.packages("xtable") command.
16 Answers
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Does Git warn me if a shorthand commit ID can refer to 2 different commits?
...g tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'
I just tested this on a real Git repository, by finding commits with duplicate prefixes like this:
git rev-list master | cut -c-4 | sort | uniq -c | sort -nr | head
Thi...
Window appears off screen on ubuntu [closed]
I have a dual monitor setup, and I am using Ubuntu 12.04 LTS
I have changed the positioning of the monitors several times, and now for some reason some of the windows open up off-screen (outside of both screens), Update Manager, for instance.
How can I position the windows on one of my screens?
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