---
title: "The lazy numbers in R: correction"
author: "Stéphane Laurent"
date: '2022-11-15'
tags: R, C++, Rcpp, maths
rbloggers: yes
output:
  md_document:
    variant: markdown
    preserve_yaml: true
  html_document:
    highlight: kate
    keep_md: no
highlighter: pandoc-solarized
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(collapse = TRUE)
```

Because of a change I did in the **lazyNumbers** package, I have to post a 
correction to 
[my previous post](https://laustep.github.io/stlahblog/posts/lazyNumbers.html).

The `as.double` function, called on a lazy number, was not stable. Now it is. 
In the previous post, the following equality was true:

```{r}
library(lazyNumbers)
x <- 1 - lazynb(7) * 0.1
as.double(x) == 0.3
```

It is not true anymore. This is expected actually. Indeed, the double numbers 
`0.1` and `0.3` do not exactly represent the numbers $0.1$ and $0.3$:

```{r}
print(0.1, digits = 17L)
print(0.3, digits = 17L)
```

The double representation of whole numbers is exact. The following equality is 
true:

```{r}
library(lazyNumbers)
x <- 1 - lazynb(7) / 10
as.double(x) == 0.3
```

No other change, and nothing else to correct. It is time to submit the package 
to CRAN. See the 
[Github repository](https://github.com/stla/lazyNumbers) for another short 
presentation of this package.