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How to drop columns using Rails migration
...ange method that can be reverted* you'll need to inform the data type (and all other field modifiers), so if you rollback that migration, the field can be correctly recreated. * When I say reverted, that's in terms of database structure, of course, data from that column obviously will be lost.
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How to overcome TypeError: unhashable type: 'list'
...used to compare dictionary keys during a dictionary lookup quickly.
Internally, hash() method calls __hash__() method of an object which are set by default for any object.
Converting a nested list to a set
>>> a = [1,2,3,4,[5,6,7],8,9]
>>> set(a)
Traceback (most recent call last...
Remove specific commit
...hanged line 2"
1 files changed, 1 insertions(+), 1 deletions(-)
Then it all works as expected.
The second answer was very interesting. There is a feature which has not yet been officially released (though it is available in Git v1.7.2-rc2) called Revert Strategy. You can invoke git like this:
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How should I have explained the difference between an Interface and an Abstract class?
...Implement the same default behavior here
// that is shared by all subclasses.
}
// Each subclass needs to provide their own implementation of this only:
public abstract void checkDBforUser();
}
Now in each child class, we only need to implement one method - the method that i...
JSTL in JSF2 Facelets… makes sense?
I would like to output a bit of Facelets code conditionally.
3 Answers
3
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What does FETCH_HEAD in Git mean?
...it like doing git fetch without arguments (or git remote update), updating all your remote branches, then running git merge origin/<branch>, but using FETCH_HEAD internally instead to refer to whatever single ref was fetched, instead of needing to name things.
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What is the difference between Flex/Lex and Yacc/Bison?
...itimate copies of (the original, AT&T versions of) Lex and Yacc to install on Ubuntu. I wouldn't necessarily say it is impossible, but I'm not aware of such. Flex and Bison are readily available and are equivalent for most purposes. You may also find various alternative and approximately equi...
Turn a simple socket into an SSL socket
...()
{
SSL_load_error_strings();
SSL_library_init();
OpenSSL_add_all_algorithms();
}
void DestroySSL()
{
ERR_free_strings();
EVP_cleanup();
}
void ShutdownSSL()
{
SSL_shutdown(cSSL);
SSL_free(cSSL);
}
Now for the bulk of the functionality. You may want to add a while lo...
Identify if a string is a number
...ld use double.TryParse, since we want to know if it represents a number at all.
– John Gietzen
May 21 '09 at 18:31
6
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Order a MySQL table by two columns
...d. When I have two columns, the name and total and want to order alphabetically by name and DESC by total, then I see only, that it was ordered by name, but not by total
– Eugene
May 3 '12 at 9:20
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