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MySQL error: key specification without a key length
...h as VARCHAR(512) will force MySQL to auto-convert the VARCHAR(512) to a SMALLTEXT datatype, which subsequently fails with error 1170 on key length if the column is used as primary key or unique or non-unique index. To solve this problem, specify a figure less than 256 as the size for VARCHAR field....
Polymorphism with gson
...mmands. The command can be start, stop , some other type of command. Naturally I have polymorphism, and start/stop command inherit from command.
...
Is double square brackets [[ ]] preferable over single square brackets [ ] in Bash?
...
[[ has fewer surprises and is generally safer to use. But it is not portable - POSIX doesn't specify what it does and only some shells support it (beside bash, I heard ksh supports it too). For example, you can do
[[ -e $b ]]
to test whether a file exists....
Why exactly is eval evil?
I know that Lisp and Scheme programmers usually say that eval should be avoided unless strictly necessary. I’ve seen the same recommendation for several programming languages, but I’ve not yet seen a list of clear arguments against the use of eval . Where can I find an account of the potentia...
Why doesn't Java Map extend Collection?
...end
Map, but this raises the question:
what are the keys? There's no really
satisfactory answer, and forcing one
leads to an unnatural interface.
Maps can be viewed as Collections (of
keys, values, or pairs), and this fact
is reflected in the three "Collection
view operations" on ...
What is href=“#” and why is it used?
...ain use of anchor tags - <a></a> - is as hyperlinks. That basically means that they take you somewhere. Hyperlinks require the href property, because it specifies a location.
Hash:
A hash - # within a hyperlink specifies an html element id to which the window should be scrolled.
hre...
Best practice for storing and protecting private API keys in applications [closed]
... time, this happens through an API key. For security purposes, services usually generate a public and private, often also referred to as secret, key. Unfortunately, in order to connect to the services, this private key must be used to authenticate and hence, probably be part of the application.
Nee...
When to use references vs. pointers
...going in undefined-behaviour-land;
the reference attribute version doesn't allow (without easy to spot tricks) the problem with 1.
the reference attribute version is simpler to understand for the user: you have to provide a valid object, not something that could be null.
If the behaviour of the fun...
Datatype for storing ip address in SQL Server
...
The technically correct way to store IPv4 is binary(4), since that is what it actually is (no, not even an INT32/INT(4), the numeric textual form that we all know and love (255.255.255.255) being just the display conversion of its binar...
SecurityError: Blocked a frame with origin from accessing a cross-origin frame
...o not use it. This else branch is
// here just for clarity, you usually shouldn't need it.
return;
}
});
This method can be applied in both directions, creating a listener in the main page too, and receiving responses from the frame. The same logic can also be implemented i...