An empty Array ([]) can be created with Array's class method, Array::new:
Array.new
To set the length of the array, pass a numerical argument:
Array.new 3 #=> [nil, nil, nil]
There are two ways to populate an array with default values:
Pass an immutable value as second argument.
P...
The groupingBy(classifier, downstream) collector allows the collection of Stream elements into a Map by classifying each element in a group and performing a downstream operation on the elements classified in the same group.
A classic example of this principle is to use a Map to count the occurrence...
This is the basic use of the <a> (anchor element) element:
<a href="http://example.com/">Link to example.com</a>
It creates a hyperlink, to the URL http://example.com/ as specified by the href (hypertext reference) attribute, with the anchor text "Link to example...
If you ignore files by using a pattern but have exceptions, prefix an exclamation mark(!) to the exception. For example:
*.txt
!important.txt
The above example instructs Git to ignore all files with the .txt extension except for files named important.txt.
If the file is in an ignored folder, y...
struct Repository {
let identifier: Int
let name: String
var description: String?
}
This defines a Repository struct with three stored properties, an integer identifier, a string name, and an optional string description. The identifier and name are constants, as they've been decla...
In order to access the value of an Optional, it needs to be unwrapped.
You can conditionally unwrap an Optional using optional binding and force unwrap an Optional using the ! operator.
Conditionally unwrapping effectively asks "Does this variable have a value?" while force unwrapping sa...
Relational operators check if a specific relation between two operands is true. The result is evaluated to 1 (which means true) or 0 (which means false). This result is often used to affect control flow (via if, while, for), but can also be stored in variables.
Equals "=="
Checks whether...
Assigns the value of the right-hand operand to the storage location named by the left-hand operand, and returns the value.
int x = 5; /* Variable x holds the value 5. Returns 5. */
char y = 'c'; /* Variable y holds the value 99. Returns 99
* (as the character 'c' is repr...
Basic Arithmetic
Return a value that is the result of applying the left hand operand to the right hand operand, using the associated mathematical operation. Normal mathematical rules of commutation apply (i.e. addition and multiplication are commutative, subtraction, division and modulus are not).
...
Logical AND
Performs a logical boolean AND-ing of the two operands returning 1 if both of the operands are non-zero. The logical AND operator is of type int.
0 && 0 /* Returns 0. */
0 && 1 /* Returns 0. */
2 && 0 /* Returns 0. */
2 && 3 /* Returns 1. */
Lo...
Getting the minimum or maximum or using sorted depends on iterations over the object. In the case of dict, the iteration is only over the keys:
adict = {'a': 3, 'b': 5, 'c': 1}
min(adict)
# Output: 'a'
max(adict)
# Output: 'c'
sorted(adict)
# Output: ['a', 'b', 'c']
To keep the dictionary ...
For every infix operator, e.g. + there is a operator-function (operator.add for +):
1 + 1
# Output: 2
from operator import add
add(1, 1)
# Output: 2
even though the main documentation states that for the arithmetic operators only numerical input is allowed it is possible:
from operator impo...
Instead of this lambda-function that calls the method explicitly:
alist = ['wolf', 'sheep', 'duck']
list(filter(lambda x: x.startswith('d'), alist)) # Keep only elements that start with 'd'
# Output: ['duck']
one could use a operator-function that does the same:
from operator import metho...
Grouping the key-value pairs of a dictionary by the value with itemgetter:
from itertools import groupby
from operator import itemgetter
adict = {'a': 1, 'b': 5, 'c': 1}
dict((i, dict(v)) for i, v in groupby(adict.items(), itemgetter(1)))
# Output: {1: {'a': 1, 'c': 1}, 5: {'b': 5}}
which ...
The Promise.all() static method accepts an iterable (e.g. an Array) of promises and returns a new promise, which resolves when all promises in the iterable have resolved, or rejects if at least one of the promises in the iterable have rejected.
// wait "millis" ms, then resolve with "...
The Promise.race() static method accepts an iterable of Promises and returns a new Promise which resolves or rejects as soon as the first of the promises in the iterable has resolved or rejected.
// wait "milliseconds" milliseconds, then resolve with "value"
function resolve(va...
Arguments are defined in parentheses after the function name:
def divide(dividend, divisor): # The names of the function and its arguments
# The arguments are available by name in the body of the function
print(dividend / divisor)
The function name and its list of arguments are called...
Optional arguments can be defined by assigning (using =) a default value to the argument-name:
def make(action='nothing'):
return action
Calling this function is possible in 3 different ways:
make("fun")
# Out: fun
make(action="sleep")
# Out: sleep
# The argumen...
One can give a function as many arguments as one wants, the only fixed rules are that each argument name must be unique and that optional arguments must be after the not-optional ones:
def func(value1, value2, optionalvalue=10):
return '{0} {1} {2}'.format(value1, value2, optionalvalue1)
Wh...
