Unlike regular functions, lambda expressions can capture their environments. Such lambdas are called closures.
// variable definition outside the lambda expression...
let lucky_number: usize = 663;
// but the our function can access it anyway, thanks to the closures
let print_lucky_number = ...
Since lambda functions are values themselves, you store them in collections, pass them to functions, etc like you would with other values.
// This function takes two integers and a function that performs some operation on the two arguments
fn apply_function<T>(a: i32, b: i32, func: T) -> ...
Returning lambdas (or closures) from functions can be tricky because they implement traits and thus their exact size is rarely known.
// Box in the return type moves the function from the stack to the heap
fn curried_adder(a: i32) -> Box<Fn(i32) -> i32> {
// 'move' applies move se...
If no ordering function is passed, std::sort will order the elements by calling operator< on pairs of elements, which must return a type contextually convertible to bool (or just bool). Basic types (integers, floats, pointers etc) have already build in comparison operators.
We can overload this ...
// Include sequence containers
#include <vector>
#include <deque>
#include <list>
// Insert sorting algorithm
#include <algorithm>
class Base {
public:
// Constructor that set variable to the value of v
Base(int v): variable(v) {
}
i...
C++11
// Include sequence containers
#include <vector>
#include <deque>
#include <list>
#include <array>
#include <forward_list>
// Include sorting algorithm
#include <algorithm>
class Base {
public:
// Constructor that set variable to the va...
To add a new unique column email to users, run the following command:
rails generate migration AddEmailToUsers email:string:uniq
This will create the following migration:
class AddEmailToUsers < ActiveRecord::Migration[5.0]
def change
add_column :users, :email, :string
add_index...
Model with ForeignKey
We will work with these models :
from django.db import models
class Book(models.Model):
name= models.CharField(max_length=50)
author = models.ForeignKey(Author)
class Author(models.Model):
name = models.CharField(max_length=50)
Suppose we often (always) access ...
It is undefined behavior to access an index that is out of bounds for an array (or standard library container for that matter, as they are all implemented using a raw array):
int array[] = {1, 2, 3, 4, 5};
array[5] = 0; // Undefined behavior
It is allowed to have a pointer pointing to the en...
pip may be used to install BeautifulSoup. To install Version 4 of BeautifulSoup, run the command:
pip install beautifulsoup4
Be aware that the package name is beautifulsoup4 instead of beautifulsoup, the latter name stands for old release, see old beautifulsoup
The default property getters and setters can be overridden:
@interface TestClass
@property NSString *someString;
@end
@implementation TestClass
// override the setter to print a message
- (void)setSomeString:(NSString *)newString {
NSLog(@"Setting someString to %@", newS...
Assuming a source file of hello_world.v and a top level module of hello_world. The code can be run using various simulators. Most simulators are compiled simulators. They require multiple steps to compile and execute.
Generally the
First step is to compile the Verilog design.
Second step is to ...
The syntax for Java generics bounded wildcards, representing the unknown type by ? is:
? extends T represents an upper bounded wildcard. The unknown type represents a type that must be a subtype of T, or type T itself.
? super T represents a lower bounded wildcard. The unknown type repres...
For programmers coming from GCC or Clang to Visual Studio, or programmers more comfortable with the command line in general, you can use the Visual C++ compiler from the command line as well as the IDE.
If you desire to compile your code from the command line in Visual Studio, you first need to set...
Group by one column
Using the following DataFrame
df = pd.DataFrame({'A': ['a', 'b', 'c', 'a', 'b', 'b'],
'B': [2, 8, 1, 4, 3, 8],
'C': [102, 98, 107, 104, 115, 87]})
df
# Output:
# A B C
# 0 a 2 102
# 1 b 8 98
# 2 c 1 107
# 3 a...
