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How do I replace NA values with zeros in an R dataframe?
...ples here: https://blog.exploratory.io/dplyr-0-5-is-awesome-heres-why-be095fd4eb8a
Attributions and Appreciations
With special thanks to:
Tyler Rinker and Akrun for demonstrating microbenchmark.
alexis_laz for working on helping me understand the use of local(), and (with Frank's patient he...
insert vs emplace vs operator[] in c++ map
...maps.)
Here's an example to demonstrate:
#include <vector>
struct foo
{
explicit foo(int);
};
int main()
{
std::vector<foo> v;
v.emplace(v.end(), 10); // Works
//v.insert(v.end(), 10); // Error, not explicit
v.insert(v.end(), foo(10)); // Also works
}
...
How do I check for nulls in an '==' operator overload without infinite recursion?
...
Use ReferenceEquals:
Foo foo1 = null;
Foo foo2 = new Foo();
Assert.IsFalse(foo1 == foo2);
public static bool operator ==(Foo foo1, Foo foo2) {
if (object.ReferenceEquals(null, foo1))
return object.ReferenceEquals(null, foo2);
ret...
深入理解 x86/x64 的中断体系 - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...[0x29]=64-Bit Interrupt Gate target=0x0010:fffff80003bf2290, DPL=0
IDT[0x2a]=64-Bit Interrupt Gate target=0x0010:fffff80003bf22a0, DPL=0
IDT[0x2b]=64-Bit Interrupt Gate target=0x0010:fffff80003bf22b0, DPL=0
IDT[0x2c]=64-Bit Interrupt Gate target=0x0010:fffff80003abca00, DPL=3
IDT[0x2d]=64-Bi...
Try-finally block prevents StackOverflowError
...(2^N) where N is the maximum stack depth.
Imagine the maximum depth is 5
foo() calls
foo() calls
foo() calls
foo() calls
foo() which fails to call foo()
finally calls
foo() which fails to call foo()
finally
foo() calls
...
How to make shallow git submodules?
... I'm getting fatal: reference is not a tree: 88fb67b07621dfed054d8d75fd50672fb26349df for each submodule
– knocte
Jan 20 '14 at 9:12
...
How to use C++ in Go
... have inheritance.
Here's an example:
I have a C++ class defined as:
// foo.hpp
class cxxFoo {
public:
int a;
cxxFoo(int _a):a(_a){};
~cxxFoo(){};
void Bar();
};
// foo.cpp
#include <iostream>
#include "foo.hpp"
void
cxxFoo::Bar(void){
std::cout<<this->a<<std::endl...
C# generic type constraint for everything nullable
...
If you are willing to make a runtime check in Foo's constructor rather than having a compile-time check, you can check if the type is not a reference or nullable type, and throw an exception if that's the case.
I realise that only having a runtime check may be unaccepta...
How to create an object for a Django model with a many to many field?
...ginal suggestion. It works, but isn't optimal. (Note: I'm using Bars and a Foo instead of Users and a Sample, but you get the idea).
bar1 = Bar.objects.get(pk=1)
bar2 = Bar.objects.get(pk=2)
foo = Foo()
foo.save()
foo.bars.add(bar1)
foo.bars.add(bar2)
It generates a whopping total of 7 queries:
...
What is the colon operator in Ruby?
...
:foo is a symbol named "foo". Symbols have the distinct feature that any two symbols named the same will be identical:
"foo".equal? "foo" # false
:foo.equal? :foo # true
This makes comparing two symbols really fast (sin...