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Regex group capture in R with multiple capture-groups
...It returns a character matrix with one column for each group in the match (and one for the whole match):
> s = c("(sometext :: 0.1231313213)", "(moretext :: 0.111222)")
> str_match(s, "\\((.*?) :: (0\\.[0-9]+)\\)")
[,1] [,2] [,3]
[1,] "(sometext ::...
boost::flat_map and its performance compared to map and unordered_map
...haven't been able to find any performance comparisons. How does it compare and what are the best use cases for it?
2 Answer...
Performance surprise with “as” and nullable types
...'m just revising chapter 4 of C# in Depth which deals with nullable types, and I'm adding a section about using the "as" operator, which allows you to write:
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ETag vs Header Expires
...d around but haven't been able to figure out if I should use both an ETag and an Expires Header or one or the other.
8 ...
Are class names in CSS selectors case sensitive?
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CSS selectors are generally case-insensitive; this includes class and ID selectors.
But HTML class names are case-sensitive (see the attribute definition), and that's causing a mismatch in your second example. This has not changed in HTML5.1
This is because the case-sensitivity of selecto...
What does the ^ operator do in Java?
...--- xor
3 = 011
This the truth table for bitwise (JLS 15.22.1) and logical (JLS 15.22.2) xor:
^ | 0 1 ^ | F T
--+----- --+-----
0 | 0 1 F | F T
1 | 1 0 T | T F
More simply, you can also think of xor as "this or that, but not both!".
See also
Wikipedia: exclusive-...
NULL values inside NOT IN clause
...t I thought were identical queries one using a not in where constraint and the other a left join . The table in the not in constraint had one null value (bad data) which caused that query to return a count of 0 records. I sort of understand why but I could use some help fully grasping the con...
Can I assume (bool)true == (int)1 for any C++ compiler?
...are redundant. In your expression:
true == 1
Integral promotion applies and the bool value will be promoted to an int and this promotion must yield 1.
Reference: 4.7 [conv.integral] / 4: If the source type is bool... true is converted to one.
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Copy a table from one database to another in Postgres
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Extract the table and pipe it directly to the target database:
pg_dump -t table_to_copy source_db | psql target_db
Note: If the other database already has the table set up, you should use the -a flag to import data only, else you may see we...
How to generate a range of numbers between two numbers?
I have two numbers as input from the user, like for example 1000 and 1050 .
28 Answers
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