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Why does += behave unexpectedly on lists?
...unction will append all elements of the parameter to the list.
When doing foo += something you're modifying the list foo in place, thus you don't change the reference that the name foo points to, but you're changing the list object directly. With foo = foo + something, you're actually creating a ne...
class
...
First, the class << foo syntax opens up foo's singleton class (eigenclass). This allows you to specialise the behaviour of methods called on that specific object.
a = 'foo'
class << a
def inspect
'"bar"'
end
end
a.inspect # =>...
SQL keys, MUL vs PRI vs UNI
...s example has neither PRI, MUL, nor UNI:
mysql> create table penguins (foo INT);
Query OK, 0 rows affected (0.01 sec)
mysql> desc penguins;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+...
Unsubscribe anonymous method in C#
... was to unsubscribe after the event was handled.
Example:
MyEventHandler foo = null;
foo = delegate(object s, MyEventArgs ev)
{
Console.WriteLine("I did it!");
MyEvent -= foo;
};
MyEvent += foo;
sh...
p vs puts in Ruby
...
p foo prints foo.inspect followed by a newline, i.e. it prints the value of inspect instead of to_s, which is more suitable for debugging (because you can e.g. tell the difference between 1, "1" and "2\b1", which you can't when...
Automatically expanding an R factor into a collection of 1/0 indicator variables for every factor le
...the ade4 package :
R> library(ade4)
R> df <-data.frame(eggs = c("foo", "foo", "bar", "bar"), ham = c("red","blue","green","red"))
R> acm.disjonctif(df)
eggs.bar eggs.foo ham.blue ham.green ham.red
1 0 1 0 0 1
2 0 1 1 0 ...
How to check if a variable is set in Bash?
...-------------+-----------------+-----------------+
| Expression | FOO="world" | FOO="" | unset FOO |
| in script: | (Set and Not Null) | (Set But Null) | (Unset) |
+--------------------+----------------------+-----------------+-----------------+
| $...
Regex: match everything but specific pattern
...t, but I think you could use a negative lookahead from the start, e.g. ^(?!foo).*$ shouldn't match anything starting with foo.
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How do you delete a column by name in data.table?
To get rid of a column named "foo" in a data.frame , I can do:
8 Answers
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How does the const constructor actually work?
... meaningful sorting order.
This means that const expressions like const Foo(1, 1) can represent any usable form that is useful for comparison in virtual machine.
The VM only needs to take into account the value type and arguments in the order in which they occur in this const expression. And, of...