uni/sose2021/r/w07/P07-3.R

# Josua Kugler, Christian Merten

library(R6)

compass <- c("N", "E", "S", "W")
movement <- list(N = c(0, 1), S = c(0, -1), W = c(-1, 0), E = c(1, 0))

# helper because R indexing beginning at 1 is stupid
get_dir <- function(k) {
    compass[(k-1) %% 4 + 1]
}

arrow_coords <- function(n, coord) {
    (coord + 0.5) / n
}

GridPath <- R6Class("GridPath", list(
    path = matrix(c(0,0), nrow=1),
    dir = character(0),
    initialize = function(dir) {
        self$dir <- dir
    },
    move = function(steps) {
        if (steps == 0) return(invisible(self))
        n <- nrow(self$path)
        self$path <- rbind(self$path,
                           self$path[n,] + movement[[self$dir]])
        self$move(steps-1)
    },
    rotate_right = function() {
        self$dir <- get_dir(which(self$dir == compass) + 1)
        invisible(self)},
    rotate_left = function() {
        self$dir <- get_dir(which(self$dir == compass) - 1)
        invisible(self)
    },
    print = function() {
        n <- max(self$path)+1
        grid <- matrix(rep(F, n^2), nrow=n)
        apply(self$path, 1, function(r) grid[r[1]+1, r[2]+1] <<- T)
        image(grid, useRaster=T, asp=T, col=c("white", "black"),
              axes=F)
        final <- self$path[nrow(self$path),]
        print(final)
        mv <- movement[[self$dir]]
        coords <- c((final)/(n-1),
                    (final + mv) / (n-1))
        arrows(coords[1], coords[2], coords[3], coords[4], col="red")
    }))

gpath3 <- GridPath$new("N")
gpath3$move(7)$
    rotate_right()$move(8)$
    rotate_right()$move(7)$
    rotate_right()$move(6)$
    rotate_right()$move(5)

gpath3