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How do I check in JavaScript if a value exists at a certain array index?
... element with index i is defined to be part of the array if i is between 0 and array.length - 1 inclusive. If i is not in this range it's not in the array.
So by concept, arrays are linear, starting with zero and going to a maximum, without any mechanism for having "gaps" inside that range where n...
Is there any significant difference between using if/else and switch-case in C#?
... (unlike many other languages) also allows to switch on string constants - and this works a bit differently. It's obviously not practical to build jump tables for strings of arbitrary lengths, so most often such switch will be compiled into stack of IFs.
But if number of conditions is big enough t...
How can I rename a database column in a Ruby on Rails migration?
...mething else or do nothing
end
end
For Rails 3.1 use:
While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".
See "Active Record...
Remove an element from a Bash array
...
The following works as you would like in bash and zsh:
$ array=(pluto pippo)
$ delete=pluto
$ echo ${array[@]/$delete}
pippo
$ array=( "${array[@]/$delete}" ) #Quotes when working with strings
If need to delete more than one element:
...
$ delete=(pluto pippo)
for de...
Jackson and generic type reference
...is a well-known problem with Java type erasure: T is just a type variable, and you must indicate actual class, usually as Class argument. Without such information, best that can be done is to use bounds; and plain T is roughly same as 'T extends Object'. And Jackson will then bind JSON Objects as Ma...
How to save and restore multiple different sessions in Vim?
...like
:mksession ~/mysession.vim
Then later you can source that vim file and you'll have your old session back:
:source ~/mysession.vim
or open vim with the -S option:
$ vim -S ~/mysession.vim
share
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How to initialise memory with new operator in C++?
I'm just beginning to get into C++ and I want to pick up some good habits. If I have just allocated an array of type int with the new operator, how can I initialise them all to 0 without looping through them all myself? Should I just use memset ? Is there a “C++” way to do it?
...
Declaring abstract method in TypeScript
...The name property is marked as protected. This was added in TypeScript 1.3 and is now firmly established.
The makeSound method is marked as abstract, as is the class. You cannot directly instantiate an Animal now, because it is abstract. This is part of TypeScript 1.6, which is now officially live....
Difference between /res and /assets directories
...le system, but I would like to know, in general, when it's best to use one and the other.
Can anyone help me in knowing the real differences between res and assets?
...
What does ON [PRIMARY] mean?
I'm creating an SQL setup script and I'm using someone else's script as an example. Here's an example of the script:
4 Ans...