41 lines
1.0 KiB
R
41 lines
1.0 KiB
R
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# Constructors
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circle <- function(r) structure(list(r=r), class="circle")
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rectangle <- function(a, b) {
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# equivalent to > structure(list(a=a, b=b), class="rectangle")
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x <- list(a=a, b=b)
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class(x) <- "rectangle"
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x # return
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}
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# generics (custom)
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area <- function(shape) UseMethod("area")
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diam <- function(shape) UseMethod("diam")
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# methods (implementation)
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print.circle <- function(circle, ...) with(circle, cat("< circle r =", r, ">\n"))
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#' Computes area of a circle object
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#'
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#' @param circle Instance of a circle.
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#'
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#' @returns Area of the given \code{circle}.
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#' @export
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area.circle <- function(circle) with(circle, pi * r^2)
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diam.circle <- function(circle) with(circle, 2 * r)
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print.rectangle <- function(rect, ...) {
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cat("<rectangle a =", rect$a, ", b =", rect$b, ">\n", set="")
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}
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area.rectangle <- function(rect) rect$a * rect$b
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diam.rectangle <- function(rect) sqrt(rect$a^2 + rect$b^2)
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# usage
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circ <- circle(2)
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rect <- rectangle(a = 1, b = 2)
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print(area(circ))
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print(diam(rect))
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print(circ)
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print(rect)
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