How to calculate the square root of a number in Ruby?

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##Introduction

First, we need to remember that it is possible to calculate the square root of a number from scratch, which it is not the case of this post.

In order to calculate the square root of a number, we're going to use the sqrt method. We can use it from the Math module or the Integer class. ]

Integer.sqrt(parameter)

Math.sqrt(parameter)

Syntax

Integer class

Integer.sqrt(number)

Math module

Math.sqrt(number)

Parameters

The Integer.sqrt() and Math.sqrt() require a non-negative number as a parameter. The Math module is going to treat the parameter as a float type, while the Integer class as an integer type.

About the Integer.sqrt(), if the parameter is not an Integer, such as a float or a string, it is going to be converted to integer first, and only after that the square root is returned. The same process happens to the Math.sqrt() method, the parameter is going to be converted to float first.

The conversion between number is a simple case scenario, the problem is when the parameter is string.

A TypeError is returned if the parameter value is a String.

irb(main):006:0> Integer.sqrt('4')
Traceback (most recent call last):
        6: from /usr/local/bin/irb:23:in `<main>'
        5: from /usr/local/bin/irb:23:in `load'
        4: from /var/lib/gems/2.5.0/gems/irb-1.1.0/exe/irb:11:in `<top (required)>'
        3: from (irb):5
        2: from (irb):6:in `rescue in irb_binding'
        1: from (irb):6:in `sqrt'
TypeError (no implicit conversion of String into Integer)
irb(main):007:0> Math.sqrt('4.0')
Traceback (most recent call last):
        6: from /usr/local/bin/irb:23:in `<main>'
        5: from /usr/local/bin/irb:23:in `load'
        4: from /var/lib/gems/2.5.0/gems/irb-1.1.0/exe/irb:11:in `<top (required)>'
        3: from (irb):6
        2: from (irb):7:in `rescue in irb_binding'
        1: from (irb):7:in `sqrt'
TypeError (can't convert String into Float)

A Math::DomainError is returned if a negative value is used as a parameter.

irb(main):001:0> Integer.sqrt(-2)
Traceback (most recent call last):
        5: from /usr/local/bin/irb:23:in `<main>'
        4: from /usr/local/bin/irb:23:in `load'
        3: from /var/lib/gems/2.5.0/gems/irb-1.1.0/exe/irb:11:in `<top (required)>'
        2: from (irb):1
        1: from (irb):1:in `sqrt'
Math::DomainError (Numerical argument is out of domain - "isqrt")
irb(main):002:0> Math.sqrt(-2)
Traceback (most recent call last):
        6: from /usr/local/bin/irb:23:in `<main>'
        5: from /usr/local/bin/irb:23:in `load'
        4: from /var/lib/gems/2.5.0/gems/irb-1.1.0/exe/irb:11:in `<top (required)>'
        3: from (irb):1
        2: from (irb):2:in `rescue in irb_binding'
        1: from (irb):2:in `sqrt'
Math::DomainError (Numerical argument is out of domain - "sqrt")

An ArgumentError is returned if the given number of parameters is different than 1, since it is expected 1 parameter.

irb(main):010:0> Integer.sqrt
Traceback (most recent call last):
        6: from /usr/local/bin/irb:23:in `<main>'
        5: from /usr/local/bin/irb:23:in `load'
        4: from /var/lib/gems/2.5.0/gems/irb-1.1.0/exe/irb:11:in `<top (required)>'
        3: from (irb):9
        2: from (irb):10:in `rescue in irb_binding'
        1: from (irb):10:in `sqrt'
ArgumentError (wrong number of arguments (given 0, expected 1))
irb(main):011:0> Math.sqrt
Traceback (most recent call last):
        6: from /usr/local/bin/irb:23:in `<main>'
        5: from /usr/local/bin/irb:23:in `load'
        4: from /var/lib/gems/2.5.0/gems/irb-1.1.0/exe/irb:11:in `<top (required)>'
        3: from (irb):10
        2: from (irb):11:in `rescue in irb_binding'
        1: from (irb):11:in `sqrt'
ArgumentError (wrong number of arguments (given 0, expected 1))

Return value

The Integer.sqrt() returns the integer square root of the non-negative integer parameter, so, as an example, the largest non-negative integer square root of 5 is 2. The method returns the largest integer number.

irb(main):001:0> Integer.sqrt(1)
=> 1
irb(main):002:0> Integer.sqrt(2)
=> 1
irb(main):003:0> Integer.sqrt(3)
=> 1
irb(main):004:0> Integer.sqrt(4)
=> 2
irb(main):005:0> Integer.sqrt(5)
=> 2

The square root of 2 is 1.4142135623730951, but this is not an integer number, so, the Integer class is going to treat it as an integer, it returns the number 1.

The Math.sqrt() is able to return a float value.

irb(main):006:0> Math.sqrt(1)
=> 1.0
irb(main):007:0> Math.sqrt(2)
=> 1.4142135623730951
irb(main):008:0> Math.sqrt(3)
=> 1.7320508075688772
irb(main):009:0> Math.sqrt(4)
=> 2.0

Conclusion

That's all for today. Let me know if you have any questions.

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