类似于R的枚举式论证

本文介绍了类似于R的枚举式论证的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 29岁程序员，3月因学历无情被辞！ 我是R的新手，目前我正在尝试向R函数（或RC / R6类方法）提供类似枚举的参数，我目前使用字符向量加$ code匹配。 arg 类似于以下内容： EnumTest = function（enum = c（BLUE RED，BLACK））{ enumArg switch（ match.arg（enum），BLUE= 0L，RED= 1L，BLACK= 2L ） switch（enumArg，＃do something ）} 是否有更好/更简洁的方式来模仿R中的类似枚举的行为？例如。一个大的问题，用户必须知道参数的一组可能的值，并手动键入它作为一个字符串 - 没有任何建议或自动完成... 如果没有其他更好的方法，有一件事情可以改进上述方法 - 通过在全球范围内预先定义枚举或者说R6类的私人成员来说，这样做可以更简洁： 颜色< - c（BLUE，RED，BLACK） 然后可以（重新）在一个或多个函数定义中使用它，例如： EnumTest = function（enum = Color）{ ... m不知道如何在 match.arg 函数中使用这个颜色矢量。如果我可以将颜色定义为一个地图，那么实际的颜色值和值就是整数表示，那么这是很好的 - 但我不知道这是多么明智。无论如何，也许存在更常见的整齐方法。 主要目标是为我的包和功能的用户提供一个易于使用的直观界面（例如，轻松找到可能的值集，tab-completion，自动建议等），然后使用枚举类的参数来定义这些函数的开发解决方案如何使用定义枚举的函数返回 list（a =a，...）？然后，您可以将返回的向量分配给变量，并在上下文中使用它，或直接使用该函数。名称或整数引用将作为索引使用，尽管您必须使用索引查找的未列出版本 [[，否则您将获得一个包含一个元素的列表。 colorEnum< - function（）{ list（BLUE =BLUE，RED =RED ，BLACK =BLACK）} colorEnum（）$ BLUE ＃> [1]BLUE colorEnum（）[[1]] ＃> [1]BLUE colorEnum（）[1] ＃> $ BLUE ＃> [1]BLUE col< - colorEnum（） col $ BLUE ＃> [1]BLUE col [[1]] ＃> [1]BLUE col $ BAD_COLOR ＃> NULL col [[5]] ＃> col [[5]]中的错误：下标超出限制 您可以获取名称列表在一个匹配中使用，即你的函数参数可以是 EnumTest = function（enum = names（colorEnum（））{.. 你也可以缩写，但它必须是唯一的（如果使用RStudio， code> col 是一个列表，它会建议完成！） col $ BLA ＃> [1]BLACK col $ BL ＃> NULL 如果你想要更复杂的枚举处理，你可以将S3类分配给你的枚举构造函数返回的东西，并在类enum上写一个小的函数集，并允许不区分大小写的索引。您还可以添加特殊功能来处理特定的类，例如colorEnum;我没有这样做。继承意味着列表访问方法仍然可以工作。 colorEnum2< - functio n（）{结构（ list（BLUE =BLUE，RED =RED，BLACK =BLACK）， class = c（colorEnum2 ，list））} ＃注意，更改示例允许多个返回值。 `[.enum`< - function（x，i）{ if（is.character（i））i< - toupper（i） class ）< - list names（as.list（x）[i]）} `[[.enum`< - function（x，i ，exact = FALSE）{ if（is.character（i））i class（x）< - list as。列表（x）[[i，exact = exact]] } `$ .enum`< - function（x，name）{x [[name] } col< - colorEnum2（）＃所有这些返回[1]RED col $ red col $ r col [[red]] col [[r]] col [red] col [c（red，BLUE ）] ＃> [1]REDBLUE col [r] [1] NA＃R不匹配部分字符串与[ 这些覆盖内置的 [， [[ / code>和 $ 函数，当索引的东西是类枚举，对于任何枚举类对象。如果你需要另外一个，你只需要定义它。 directionEnum< - function（）{结构（列表（LEFT =LEFT RIGHT =RIGHT）， class = c（directionEnum，enum，list））} directionEnum（）$ l ＃> [1]LEFT 如果您需要几个枚举对象，可以添加工厂函数枚举，它需要一个字符串和名称的向量，并返回一个枚举对象。大部分只是验证。 枚举< - function（enums，name = NULL）{ if长度（枚举）< 1） stop（枚举可能不为空）枚举< - toupper（as.character（enums）） uniqueEnums< - unique枚举）如果（！same（enums，uniqueEnums）） stop（枚举必须是唯一的（忽略大小写）） validNames< - make.names（enums） if（！identical（enums，validNames）） stop（枚举必须是有效的R标识符） enumClass< - c（name，枚举，列表） obj< - as.list（枚举）名称（obj）< - 枚举结构（obj，class = enumClass）} col< - enum（c（BLUE，red，Black），name =TheColors） col $ R ＃> [1]RED class（col）＃> [1]TheColorsenumlist side< - enum（c（left，right）） side $ L ＃> ; [1]LEFT class（s​​ide）＃> [1]枚举列表 但是现在开始看起来像一个包.. 。 I'm new to R and I'm currently trying to supply the enumeration-like argument to the R function (or the RC/R6 class method), I currently use character vector plus match.arg similar to the following:EnumTest = function(enum = c("BLUE", "RED", "BLACK")) { enumArg <- switch( match.arg(enum), "BLUE" = 0L, "RED" = 1L, "BLACK" = 2L ) switch(enumArg, # do something )}Is there are better/more concise way to imitate enum-like behavior in R? E.g. one big problem that user has to know the set of possible values for the argument and manually type it as a string - without any suggestion or auto-completion...If there is no other better way, one thing that could improve above approach - it'd be nice to make it more concise by say predefining enums globally or say as private members of R6 class:Color <- c("BLUE", "RED", "BLACK")Then one could (re)use it in one or more function definitions, e.g.:EnumTest = function(enum = Color) {...However, I'm not sure how to use this Color vector in match.arg function. It'd be nice if I could define Color as a map with keys being actual color values and values being integer representation - but I'm not sure how sensible that is.. Anyways, maybe there are more common neat approaches exist.The main goal would be to provide an easy-to-use intuitive interface to the user of my package and functions (e.g. easy way to find the set of possible values, tab-completion, auto-suggestion, etc..), followed by standardized development of such functions using enum-like arguments 解决方案 How about using a function that defines the enum by returning list(a= "a", ...)? You can then either assign the returned vector to a variable and use it in context, or use the function directly. Either a name or an integer reference will work as an index, although you have to use the unlist version of the index lookup, [[, otherwise you get a list with one element.colorEnum <- function() { list(BLUE = "BLUE", RED = "RED", BLACK = "BLACK")}colorEnum()$BLUE#> [1] "BLUE"colorEnum()[[1]]#> [1] "BLUE"colorEnum()[1]#> $BLUE#> [1] "BLUE"col <- colorEnum()col$BLUE#> [1] "BLUE"col[[1]]#> [1] "BLUE"col$BAD_COLOR#> NULLcol[[5]]#> Error in col[[5]] : subscript out of boundsYou can get the list of names for use in a match, i.e. your function parameter could beEnumTest = function( enum = names(colorEnum()) { ...You can actually abbreviate too, but it must be unique. (If you use RStudio, since col is a list, it will suggest completions!)col$BLA#> [1] "BLACK"col$BL#> NULLIf you want more sophisticated enum handling, you could assign S3 classes to the thing returned by your enum constructor function and write a small collection of functions to dispatch on class "enum" and allow case-insensitive indexing. You could also add special functions to work with a specific class, e.g. "colorEnum"; I have not done that here. Inheritance means the list access methods all still work.colorEnum2 <- function() { structure( list(BLUE = "BLUE", RED = "RED", BLACK = "BLACK"), class= c("colorEnum2", "enum", "list") )}# Note, changed example to allow multiple returned values.`[.enum` <- function(x, i) { if ( is.character( i )) i <- toupper(i) class(x) <- "list" names(as.list(x)[i])}`[[.enum` <- function(x, i, exact= FALSE) { if ( is.character( i )) i <- toupper(i) class(x) <- "list" as.list(x)[[i, exact=exact]]}`$.enum` <- function(x, name) { x[[name]]}col <- colorEnum2()# All these return [1] "RED"col$redcol$rcol[["red"]]col[["r"]]col["red"]col[c("red", "BLUE")]#> [1] "RED" "BLUE"col["r"][1] NA # R does not matches partial strings with "["These override the built in [, [[ and $ functions when the thing being indexed is of class "enum", for any "enum" classed objects. If you need another one, you just need to define it. directionEnum <- function() { structure( list(LEFT = "LEFT", RIGHT = "RIGHT"), class= c("directionEnum", "enum", "list") )}directionEnum()$l#> [1] "LEFT"If you need several enum objects, you could add a factory function enum that takes a vector of strings and a name and returns an enum object. Most of this is just validation.enum <- function(enums, name= NULL) { if (length(enums) < 1) stop ("Enums may not be empty." ) enums <- toupper(as.character(enums)) uniqueEnums <- unique(enums) if ( ! identical( enums, uniqueEnums )) stop ("Enums must be unique (ignoring case)." ) validNames <- make.names(enums) if ( ! identical( enums, validNames )) stop( "Enums must be valid R identifiers." ) enumClass <- c(name, "enum", "list") obj <- as.list(enums) names(obj) <- enums structure( obj, class= enumClass)}col <- enum(c("BLUE", "red", "Black"), name = "TheColors")col$R#> [1] "RED"class(col)#> [1] "TheColors" "enum" "list"side <- enum(c("left", "right"))side$L#> [1] "LEFT"class(side)#> [1] "enum" "list"But now this is starting to look like a package... 这篇关于类似于R的枚举式论证的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！