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Adding :default => true to boolean in existing Rails column
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change_column is a method of ActiveRecord::Migration, so you can't call it like that in the console.
If you want to add a default value for this column, create a new migration:
rails g migration add_default_value_to_show_attribute
Then in the migration created:
# That's the more generic way t...
Arduino Sketch upload issue - avrdude: stk500_recv(): programmer is not responding
...it works. I figured the packets were some attempt at a hand-shake. So basically, I solved it using Google, patience and futzing around with the board!
– hoipolloi
Jan 12 '14 at 18:16
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C++ Lock-free Hazard Pointer（冒险指针） - C/C++ - 清泛网 - 专注C/C++及内核技术
...std::memory_order_acquire); p; p = p->next_) {
if (!p->active_.test_and_set()) {
return p;
}
}
auto p = new HazardPointer<T>();
p->active_.test_and_set();
do {
p->next_ = head_list_.load(std::memory_order_acquire);
} while (!head_list_.compare...
Environment variable to control java.io.tmpdir?
...s.
On Windows, OpenJDK's get_temp_directory() function makes a Win32 API call to GetTempPath(); this is how on Windows, Java reflects the value of the TMP environment variable.
On Linux and Solaris, the same get_temp_directory() functions return a static value of /tmp/.
I don't know if the actual...
`staticmethod` and `abc.abstractmethod`: Will it blend?
In my Python app I want to make a method that is both a staticmethod and an abc.abstractmethod . How do I do this?
4 Ans...
What is the most “pythonic” way to iterate over a list in chunks?
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Finally got a chance to play around with this in a python session. For those who are as confused as I was, this is feeding the same iterator to izip_longest multiple times, causing it to consume successive values of the same seq...
Google breakpad stackwalker无法加载符号 - 更多技术 - 清泛网 - 专注C/C++及内核技术
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参考：https://stackoverflow.com/questions/23537187/stackwalker-loads-all-symbol-files-but-still-doesnt-symbolicate-anything
How to prevent a jQuery Ajax request from caching in Internet Explorer?
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You can disable caching globally using $.ajaxSetup(), for example:
$.ajaxSetup({ cache: false });
This appends a timestamp to the querystring when making the request. To turn cache off for a particular $.ajax() call, set cache: false on it locally, ...
Pandas convert dataframe to array of tuples
...ou want normal tuples in your zip iterator (instead of namedtuples), then call: data_set.itertuples(index=False, name=None)
– Axel
Oct 25 '17 at 9:47
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What are the GCC default include directories?
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There is a command with a shorter output, which allows to automatically cut the include pathes from lines, starting with a single space:
$ echo | gcc -Wp,-v -x c++ - -fsyntax-only
ignoring nonexistent directory "/usr/lib/gcc/x86_64-redhat-linux/4.8.2/include-fixed"
ignori...