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https://github.com/jonocarroll/weasel
Provides `pop()` and `push()` functionality
https://github.com/jonocarroll/weasel
Last synced: 8 days ago
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Provides `pop()` and `push()` functionality
- Host: GitHub
- URL: https://github.com/jonocarroll/weasel
- Owner: jonocarroll
- License: other
- Created: 2023-06-09T06:32:33.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2023-06-10T01:52:40.000Z (over 1 year ago)
- Last Synced: 2024-11-15T14:42:59.961Z (2 months ago)
- Language: R
- Homepage:
- Size: 56.6 KB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.Rmd
- Funding: .github/FUNDING.yml
- License: LICENSE
Awesome Lists containing this project
README
---
output: github_document
---
```{r, include = FALSE}
knitr::opts_chunk$set(
collapse = TRUE,
comment = "#>",
fig.path = "man/figures/README-",
out.width = "100%"
)
library(weasel)
```
# weasel 
> *'Round and 'round the R workspace, code-monkey chased the {weasel}*
>
> *Code-monkey stopped to extract the first val...*
>
> *`pop()` goes the {weasel}*
## Installation
You can install the development version of weasel like so:
``` r
# install.packages("remotes")
remotes::install_github("jonocarroll/weasel")
```
## Motivation
Inspired by other (less functional/immutable) languages where one might be
familiar with being able to `pop()` a value from the top of the stack, this
package provides similar functionality.
If we define a vector `a` containing some values
```{r}
a <- c(3, 1, 4, 1, 5, 9)
```
and we wish to extract the first value, we can certainly do so with
```{r}
a[1]
```
but, due to the nature of R, the vector `a` is unchanged
```{r}
a
```
Instead, we could remove the first value of `a` with
```{r}
a[-1]
```
but again, `a` remains unchanged - in order to modify `a` we must redefine it as e.g.
```{r}
a <- a[-1]
a
```
This differs from other languages were we might want to _extract_ that first value for use,
and leave the rest of the vector in place.
## Usage
{weasel} offers that functionality
```{r}
a <- c(3, 1, 4, 1, 5, 9)
a
first_val <- pop(a)
a
first_val
```
Note that this did not require explicitly^[It certainly is redefined internally, but
the use of `defmacro()` means it does not need to be explicit] redefining `a`;
the return value of `pop()` is the popped value.
This is also a Generic, so it is defined for some classes (`vector`, `list`, `data.frame`)
and can be extended.
With a `list`:
```{r}
a <- list(x = c(2, 3), y = c("foo", "bar"), z = c(3.1, 4.2, 6.9))
a
x <- pop(a)
a
x
```
With a `data.frame`:
```{r}
a <- data.frame(x = c(2, 3, 4), y = c("foo", "bar", "baz"), z = c(3.1, 4.2, 6.9))
a
x <- pop(a)
a
x
```
{weasel} also offers `push()` functionality
```{r}
a <- c(1, 4, 1, 5, 9)
a
push(a, 3)
a
```
which is also Generic
```{r}
a <- list(y = c("foo", "bar"), z = c(3.1, 4.2, 6.9))
a
push(a, list(new_vals = c(99, 77)))
a
a <- data.frame(y = c("foo", "bar", "baz"), z = c(3.1, 4.2, 6.9))
a
push(a, data.frame(y = 99, z = 77))
a
```
## Warnings
Please note that this is intended only for informal use and education. This
functionality is **not** idiomatic R and is more of a footgun than should be
tolerated.
## Explanation
Internally, the evaluation of each 'method' is a macro defined using `gtools::defmacro()`
which enables substitution of input arguments and redefinition in the parent namespace.
[This blogpost](https://jcarroll.com.au/2023/06/10/reflecting-on-macros/) covers the full details. [This article](https://www.r-project.org/doc/Rnews/Rnews_2001-3.pdf) in the R News Newsletter
covers the construction and motivation of `defmacro()`.