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map vs. hash_map in C++
...tied to that key.
map is implemented as a balanced binary search tree (usually a red/black tree).
An unordered_map should give slightly better performance for accessing known elements of the collection, but a map will have additional useful characteristics (e.g. it is stored in sorted order, which...
What is the Python equivalent of static variables inside a function?
...
there is only one instance of foo - this one function. all invocations access the same variable.
– Claudiu
Nov 10 '08 at 23:49
124
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Why are quaternions used for rotations?
... multiplication is much faster than 3x3 matrix multiplication).
Note that all of these representations of rotations are used in practice. Euler angles use the least memory; matrices use more memory but don't suffer from Gimbal lock and have nice analytical properties; and quaternions strike a nice ...
How do I remove the file suffix and path portion from a path string in Bash?
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This is probably the most flexible of all the answers posted, but I think the answers suggesting the basename and dirname commands deserve some attention as well. They may be just the trick if you don't need any other fancy pattern matching.
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Cleaning `Inf` values from an R dataframe
...ption 1
Use the fact that a data.frame is a list of columns, then use do.call to recreate a data.frame.
do.call(data.frame,lapply(DT, function(x) replace(x, is.infinite(x),NA)))
Option 2 -- data.table
You could use data.table and set. This avoids some internal copying.
DT <- data.table(dat)...
GLib compile error (ffi.h), but libffi is installed
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If you have a Debian-based Linux OS with apt-get:
sudo apt-get install libffi-dev
With a Redhat-base OS:
yum install libffi-devel
With Alpine Linux:
apk add libffi-dev
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Add a column with a default value to an existing table in SQL Server
...ed for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES or not.
How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it...
How to see query history in SQL Server Management Studio
...tary format. However if you need to see queries that were executed historically (except SELECT) this is the only way.
You can use third party tools for this such as ApexSQL Log and SQL Log Rescue (free but SQL 2000 only). Check out this thread for more details here SQL Server Transaction Log Explo...
How to delete a row by reference in data.table?
...nce yet.
data.table can add and delete columns by reference since it over-allocates the vector of column pointers, as you know. The plan is to do something similar for rows and allow fast insert and delete. A row delete would use memmove in C to budge up the items (in each and every column) after t...
How to add a vertical Separator?
...tretch" Width="1" Margin="2" Stroke="Black" />
<Button>Filter all</Button>
</StackPanel>
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