[JAVA] Part 1 Attempt to code mathematics (∈)

This post is a Japanese translation of Mathematics to code: ∈-by Kohei Shingai.

is.element.of.2.jpg

is.element.of.1.jpg https://www.instagram.com/p/BQvOfRygJCA

Check x ∈ A with a function of R

Use ʻis.element (x, A)`,

A <- c(1:5)
#Set A is[1, 2, 3, 4, 5]

is.element(1, A) #result: TRUE
#That is, 1 ∈ A- {1, 2, 3, 4, 5}whether?

is.element(6, A) #result: FALSE
#That is, 6 ∈ A- {1, 2, 3, 4, 5}whether?

Check x ∈ A with standard Python operators

Use x in A,

A = set([1, 2, 3, 4, 5]) #Set A

1 in A #result: True
#That is, 1 ∈ A- {1, 2, 3, 4, 5}whether?

6 in A #result: False
#That is, 6 ∈ A- {1, 2, 3, 4, 5}whether?

Check x ∈ A in Ruby method

Use ʻA.include? X`,

A = (1..5).to_a
#Set A is[1, 2, 3, 4, 5]

A.include?1 #result: true
#That is, 1 ∈ A- {1, 2, 3, 4, 5}whether?

A.include?6 #result: false
#That is, 6 ∈ A- {1, 2, 3, 4, 5}whether?

Check x ∈ A in a JavaScript expression or method

Use ʻA.indexOf ()! = -1 or ʻA.includes (x),

A = [1, 2, 3, 4, 5] //Set A

A.indexOf(1) != -1 //result: true
//That is, 1 ∈ A- {1, 2, 3, 4, 5}whether?

A.indexOf(6) != -1 //result: false
//That is, 6 ∈ A- {1, 2, 3, 4, 5}whether?

A.includes(1) //result: true -ES2016 or later
//That is, 1 ∈ A- {1, 2, 3, 4, 5}whether?

A.includes(6) //result: false -ES2016 or later
//That is, 6 ∈ A- {1, 2, 3, 4, 5}whether?