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How can I check for “undefined” in JavaScript? [duplicate]
... property was declared but just not initialized. Use the in operator for a more robust check.
"theFu" in window; // true
"theFoo" in window; // false
If you are interested in knowing whether the variable hasn't been declared or has the value undefined, then use the typeof operator, which is guara...
How can I rename a database column in a Ruby on Rails migration?
...need to write a separate down method".
See "Active Record Migrations" for more information.
rails g migration FixColumnName
class FixColumnName < ActiveRecord::Migration
def change
rename_column :table_name, :old_column, :new_column
end
end
If you happen to have a whole bunch of colu...
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An efficient compression algorithm for short text strings [closed]
...ay (e.g. all URLs, all C programs, all StackOverflow posts, all ASCII-art drawings) then certain substrings will appear in most or all of the input files.
Every compression algorithm will save space if the same substring is repeated multiple times in one input file (e.g. "the" in English text or "...
Difference between string and char[] types in C++
...will always have the overhead of a heap allocation.
If you copy a text of more than 256 chars into the array, it might crash, produce ugly assertion messages or cause unexplainable (mis-)behavior somewhere else in your program.
To determine the text's length, the array has to be scanned, character ...
How to count the number of true elements in a NumPy bool array
...gt;>> np.sum(boolarr)
5
Of course, that is a bool-specific answer. More generally, you can use numpy.count_nonzero.
>>> np.count_nonzero(boolarr)
5
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Docker - a way to give access to a host USB or serial device?
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How to make an HTTP POST web request
...ey are not deprecated, there are just newer (and is most cases, better and more flexible) ways of making web requests. In my opinion, for simple, non-critical operations, the old ways are just fine - but it's up to you and whatever you are most comfortable with.
– Evan Mulawski...
What are the differences between struct and class in C++?
...d when the class is declared class.
And just for completeness' sake, the more widely known difference between class and struct is defined in (11.2):
Member of a class defined with the
keyword class are private by
default. Members of a class defined
with the keywords struct or union
are...
How to create a trie in Python
...I'll add that creating a directed acyclic word graph (DAWG) would be a bit more complex, because you have to detect situations in which your current word shares a suffix with another word in the structure. In fact, this can get rather complex, depending on how you want to structure the DAWG! You may...