In this shot, we will learn how to use the `ratio_less()` function. The **`ratio_less()`** function is available in the `<ratio>` header file in C++. This template alias is used to check whether the first ratio object is less than the second ratio object or not and gives the boolean value as a result, i.e., either *true* or *false*. The `ratio_less()` method compares the simplest forms of the two ratios.

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## What is a ratio?
A **ratio** is a representation of a fraction in which the numerator and denominator are differentiated by the *colon (:)* symbol. The numerator and denominator can be of `float` data type.

Let’s understand with the help of some examples. 

* Suppose that the first ratio is $1 : 5$ and the second ratio is $1 : 2$.
* The result of the `ratio_less()` function is `true`. 

Let’s dive into how the *less than inequality* check took place.

* The ratios $1 : 5$ and $1 : 2$ can be represented as $\frac{1}{5}$ and $\frac{1}{2}$ in fractional form, respectively.
* Both the ratios are already simplified. 
* Now, the simplified fractions, i.e., $\frac{1}{5}$ and $\frac{1}{2}$,  are compared.  

* We can see that the first ratio is less than the second ratio, and we get the final result as *true*.


## Parameters

* Ratio 1: A `ratio` object to be compared for less than inequality with the other ratio object.
* Ratio 2: Another `ratio` object that gets compared for the less than inequality with the previous ratio object.

## Return value
`ratio_less()` returns the boolean result after comparison for less than inequality.
* If the first ratio object is less than the second ratio object, then `ratio_less()` returns `true`.

* If the first ratio object is not less than the second ratio object, then `ratio_less()` returns `false`.

## Code
Let’s have a look at the code.

#include <iostream>
#include <ratio>
using namespace std;

int main()
{
  typedef ratio<1, 5> ratio_one;
  typedef ratio<1, 5> ratio_two;
  
  if (ratio_less<ratio_one, ratio_two>::value)
    cout<<"The ratio_one is less than the ratio_two";
  else
    cout<<"The ratio_one is not less than the ratio_two";
  
  return 0;
}


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## Explanation
* In lines 1 and 2, we import the required header files.
* In line 5, we make a `main()` function.

* From lines 7 and 8, we declare the two ratios.
* In line 10, we use the `ratio_less()` function inside the `if` statement to perform the comparison between the two declared ratios. If the first ratio object is less than the second ratio object, then the `if` statement gets executed and displays the message with the result. Here, `value` is a member variable of the `ratio` class.
* In line 12, if the condition doesn’t satisfy, i.e., the first ratio object is not less than the second ratio object, then the `else` statement gets executed and displays the message with the result.

We can use the `ratio_less()` function to check whether the first ratio object is less than the second ratio object.



How to use the ratio_less() function in C++

The `ratio_less()` function in C++ compares two ratio objects and returns a boolean indicating if the first ratio is less than the second.