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Rails migration for change column
...l situations where the existing data, let's say a String can be implicitly converted into the new datatype, let's say Date.
In this situation, it's helpful to know you can create migrations with data conversions. Personally, I like putting these in my model file, and then removing them after all d...
How to compare binary files to check if they are the same?
...
I ended up using hexdump to convert the binary files to there hex representation and then opened them in meld / kompare / any other diff tool. Unlike you I was after the differences in the files.
hexdump tmp/Circle_24.png > tmp/hex1.txt
hexdump /tmp...
Sequence-zip function for c++11?
...
Warning: boost::zip_iterator and boost::combine as of Boost 1.63.0 (2016 Dec 26) will cause undefined behavior if the length of the input containers are not the same (it may crash or iterate beyond the end).
Starting from Boost 1.56.0 (2014 Aug 7) you...
Thread pooling in C++11
...r function with an infinite loop, constantly waiting for new tasks to grab and run.
Here is how to attach such function to the thread pool:
int Num_Threads = thread::hardware_concurrency();
vector<thread> Pool;
for(int ii = 0; ii < Num_Threads; ii++)
{ Pool.push_back(thread(Infinite_loop...
Default initialization of std::array?
...zed (C++11 §8.5/11). That includes objects of type std::array<T, N> and T[N].
Be aware that there are types for which default initialization has no effect and leaves the object's value indeterminate: any non-class, non-array type (§8.5/6). Consequently, a default-initialized array of object...
What does the unary plus operator do?
... plus operator do? There are several definitions that I have found ( here and here ) but I still have no idea what it would be used for. It seems like it doesn't do anything but there has be a reason for it, right?
...
How to access command line parameters?
...econd iterated element.
An easy way to deal with the result of args is to convert it to a Vec:
use std::env;
fn main() {
let args: Vec<_> = env::args().collect();
if args.len() > 1 {
println!("The first argument is {}", args[1]);
}
}
You can use the whole standard i...
Why aren't variable-length arrays part of the C++ standard?
... space available, isn't good. The argument is, if you know the size beforehand, you can use a static array. And if you don't know the size beforehand, you will write unsafe code.
C99 VLAs could provide a small benefit of being able to create small arrays without wasting space or calling constructo...
Can a recursive function be inline?
...s , found that the above code would lead to "infinite compilation" if not handled by compiler correctly.
9 Answers
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How to overcome TypeError: unhashable type: 'list'
...the other answers, the error is to due to k = list[0:j], where your key is converted to a list. One thing you could try is reworking your code to take advantage of the split function:
# Using with ensures that the file is properly closed when you're done
with open('filename.txt', 'rb') as f:
d = ...