add s4 emojis to pdf, replace r6 emojis

- #257

14_R6.Rmd

@@ -118,11 +118,13 @@ my_charging_account$balance
 __[Q2]{.Q}__: Create an R6 class that represents a shuffled deck of cards. You should be able to draw cards from the deck with `$draw(n)`, and return all cards to the deck and reshuffle with `$reshuffle()`. Use the following code to make a vector of cards.
 
 ```{r}
-suit <- c("♠", "♥", "♦", "♣")
+suit <- c("SPADE", "HEARTS", "DIAMOND", "CLUB")
 value <- c("A", 2:10, "J", "Q", "K")
-cards <- paste0(rep(value, 4), suit)
+cards <- paste(rep(value, 4), suit)
 ```
 
+*(This question was altered slightly to avoid the unicode characters.)*
+
 __[A]{.solved}__: Our new `ShuffledDeck` class will use `sample()` and positive integer subsetting to implement the reshuffling and drawing functionality. We also add a check, so you cannot draw more cards than there are left in the deck.
 
 ```{r}

15_S4.Rmd

@@ -285,15 +285,20 @@ setMethod("show", "Person", function(object, y) {
 ## Method dispatch 
 <!-- 15.5 -->
 
-__[Q1]{.Q}__: Draw the method graph for `f(😅, 😽)`.
+```{r, include=FALSE}
+source("emoji.R")
+code <- function(...) paste0("`", ..., "`")
+```
+
+__[Q1]{.Q}__: Draw the method graph for `r paste0(code("f("), emoji("sweat_smile"), ", ", emoji("kissing_cat"), code(")"))`.
 
 __[A]{.solved}__: Look at the graph and repeat after me: "I will keep my class structure simple and use multiple inheritance sparingly".
 
 ```{r, echo = FALSE, out.width='350pt'}
 knitr::include_graphics("images/s4/method_dispatch1.png", dpi = 300)
 ```
 
-__[Q2]{.Q}__: Draw the method graph for `f(😃, 😉, 😙)`.
+__[Q2]{.Q}__: Draw the method graph for `r paste0(code("f("), emoji("smiley"), ", ", emoji("wink"), ", ", emoji("kissing_smiling_eyes"), code(")"))`.
 
 __[A]{.solved}__: We see that the method graph below looks simpler than the one above. Relatively speaking, multiple dispatch seems to introduce less complexity than multiple inheritance. Use it with care, though!