---
title: "Use Cases"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Use Cases}
  %\VignetteEncoding{UTF-8}
  %\VignetteEngine{knitr::rmarkdown}
editor_options: 
  chunk_output_type: console
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

The following examples demonstrate using `chars` objects inside functions, no 
longer needing to spell out `strsplit(x, "")[[1]]` every time. 

```{r setup}
library(charcuterie)
```

## Test Membership

Which letters are vowels (aeiou)?

```{r}
vowels <- function(word) {
  ch <- chars(word)
  setNames(ch %in% chars("aeiou"), ch)
}
vowels("string")
vowels("banana")
```

Since `%in%` is vectorised, it works nicely with a `chars` object

```{r}
banana <- chars("banana")
banana[which(banana %in% chars("aeiou"))]

onomatopoeia <- chars("onomatopoeia")
onomatopoeia[which(onomatopoeia %in% chars("aeiou"))]
```

## Iterate

"Strings" are finally iterable 

```{r}
for (x in chars("ABC")) {
  print(paste("Appendix", x))
}
```

## Identify Palindromes

Is a word a palindrome (spelled the same forwards and backwards)?

```{r}
palindrome <- function(a, ignore_spaces = FALSE) {
  a <- chars(a)
  if (ignore_spaces) a <- except(a, " ")
  all(rev(a) == a)
}
palindrome("palindrome")
palindrome("racecar")
palindrome("never odd or even", ignore_spaces = TRUE)
palindrome("go hang a salami im a lasagna hog", ignore_spaces = TRUE)
```

## Find Anagrams

Are two words just rearrangements of their letters?

```{r}
anagram <- function(a, b) {
  is_anagram <- function(a, b) {
    length(a) == length(b) && all(sort(a) == sort(b))
  }
  sapply(candidates, \(x) is_anagram(chars(a), chars(x)))
}
target <- "stressed"
candidates <- c("started", "desserts", "rested")
anagram(target, candidates)
```

## Spongebob Case

Make every second letter uppercase

```{r}
spongebob <- function(phrase) {
  x <- chars(phrase)
  odds <- seq(1, length(x), 2)
  x[odds] <- toupper(x[odds])
  string(x)
}
spongebob("you can't do anything useful with this package")
```

```{r, echo=FALSE}
knitr::include_graphics("spongebob.jpg")
```