Let's see how to count the number of elements in an array in some languages [Go, JavaScript, PHP, Python, Ruby, Swift]

Recently, I have come into contact with several languages in my work, and when I go back and forth between multiple languages, the simple syntax may get confused.

For the sake of organizing my mind, this time I will look at how to count the number of elements in an array in some languages.

All of them are shallow, so I hope that professionals in each language will take a calm look. : pray:

Appearance language

• Go
• JavaScript
• PHP
• Python
• Ruby
• Swift

▶︎ Go

The Go language provides len () as a built-in function. Therefore, you can get the number of elements in the array in the form len (array).

Also, in Go, there are Array type and Slice type as array-like types, The Array type of Go has a fixed number of elements, and it seems that the Slice type is closer when used like an array in other languages. Therefore, Slice is also used in the following code example.

Code example

package main

import (
	"fmt"
)

func main() {

	languages := []string{"Go", "JavaScript", "PHP", "Python", "Ruby", "Swift"}
	fmt.Println(len(languages)) // -> 6

}

Go Playground: https://play.golang.org/p/r6yPBOU5uC

(Author execution version: Runtime version of Go Playfround → https://play.golang.org/p/1VcPUlPk_3)

Supplement

In addition to Array and Slice, map, String, Channel, etc. can be taken as the argument of len, and it seems that the length that matches the type is returned. (Array and map are the number of elements, String is the number of bytes, etc.)

reference

https://golang.org/pkg/builtin/#len

▶︎ JavaScript

In JavaScript, Array has a length property. Therefore, you can get the number of elements with ʻarray.length`.

Code example

var languages = ["Go", "JavaScript", "PHP", "Python", "Ruby", "Swift"];
console.log(languages.length); // -> 6

Supplement

It is the length property of Array, but it seems that it is writable, and if you shorten the length, the elements in the array also change. I knew this for the first time.

languages.length = 3;
console.log(languages); // -> ["Go", "JavaScript", "PHP"]

reference

https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Array/length

▶︎ PHP

PHP provides a function called count (). Therefore, you can get the number of elements in the array in the form count ($ array).

Code example

$languages = array("Go", "JavaScript", "PHP", "Python", "Ruby", "Swift");
// PHP 5.After 4 it is OK to write as below
// $languages = ["Go", "JavaScript", "PHP", "Python", "Ruby", "Swift"];
echo(count($languages)); // -> 6

(Author running version: PHP 5.3.27) Old. Lol

Supplement

There is also an alias for count () called sizeof (), so it's exactly the same.

It's similar to Go in passing an array as an argument to a built-in function, but unlike Go, passing a String doesn't return the number of bytes.

reference

http://php.net/manual/ja/function.count.php

▶︎ Python

In Python, the word array is not used in the first place, and the equivalent of an array is called a list. To get the number of elements in the list, use the built-in function len ().

Code example

languages = ["Go", "JavaScript", "PHP", "Python", "Ruby", "Swift"]
print len(languages) # -> 6

(Author execution version: Python 2.7.12)

Supplement

In the reference

Arguments can be sequences (strings, bytes, tuples, lists, ranges, etc.) or collections (dictionaries, sets, frozen sets, etc.).

So, this is similar to Go, and you can see that it returns the length of each other than the list.

reference

2 system http://docs.python.jp/2/library/functions.html#len 3 series http://docs.python.jp/3/library/functions.html#len

▶︎ Ruby

In Ruby, the Array class has a length method and asize method, both of which can get the number of elements. (The size method seems to be an alias for the length method)

Also, since the Enumerable module included in the Array class has a count method, you can get the number of elements in the array by using the count method with no arguments in the Array class as well.

Code example

languages = ["Go", "JavaScript", "PHP", "Python", "Ruby", "Swift"]
p languages.length # -> 6
p languages.size # -> 6
p languages.count # -> 6

(Author execution version: ruby 2.3.0)

Supplement

I think the following article will be helpful for the difference between the length method and the count method. http://qiita.com/saino-katsutoshi/items/7d761c026563a649d046

reference

http://ruby-doc.org/core-2.3.0/Array.html#method-i-length

▶︎ Swift

In Swift, the Array structure has a count property, so you can get the number of elements from this count property.

Code example

let languages = ["Go", "JavaScript", "PHP", "Python", "Ruby", "Swift"]
print(languages.count) // -> 6

(Author execution version: Swift 3.0)

Supplement

The Array structure conforms to the Collection protocol, so the count property must be defined. It's also similar to JavaScript's length property in terms of properties, but Swift's count property is read-only, so you can't rewrite its value.

reference

https://developer.apple.com/reference/swift/array/1539982-count

Summary

First of all,

--Language where functions / properties that return the number of elements in the array class (etc.) are defined, such as ʻarray_object.count_method_or_property**, and --Language that has a function that returns the length of the object passed as an argument as a built-in function ** likecount_function (array_object)` **

There seems to be.

Furthermore, even if it is divided, "property or method" is different, and "whether the content of the value returned depends on the type passed to the argument" is different depending on the language.

It's interesting that it depends on the language whether or not the array object keeps track of the number of its elements.

Also, there are still many parts that I haven't learned deeply about each language, so I'll study little by little.