将函数参数传递给其他本身就是函数的参数 [英] Passing a function argument to other arguments which are functions themselves

问题描述

假定我有一个外部函数，该函数具有一个数字参数和一个本身就是函数的参数(内部函数).如何将外部函数的数字参数的值作为内部函数的参数传递?考虑这个玩具示例:

Assume I have an outer function that has a numeric argument and an argument which is a function itself (inner function). How can I pass the value of the numeric argument of the outer function as an argument to the inner function? Consider this toy example:

innerfun <- function(M){
 1:M
}

outerfun <- function(x, fun){
 x * fun
}

outerfun(x = 3, fun = innerfun(M = 3)) ## works
outerfun(x = 3, fun = innerfun(M = x)) ## error because innerfun can't find 'x'
outerfun(x = 3, fun = innerfun(M = get("x"))) ## doesn't work either...

所以我想做的是在评估externalfun的参数时调用innerfun，使用对innerfun的调用中的这些externalfun参数.有什么想法或建议吗?

So what I want to do is to call innerfun at the moment the arguments of outerfun are evaluated, using those outerfun-arguments in the call to innerfun. Any ideas or suggestions?

推荐答案

我会做这样的事情:

outerfun <- function(x, fun,...){
  x * fun(x,...)
}
innerfun <- function(M){
  seq_len(M) ## safer than 1:M
}
outerfun(x=3, innerfun)
[1] 3 6 9

请注意，如果内部函数具有多个参数，则它仍然有效:

Note that If inner function has more than one argument, it still works :

innerfun2 <- function(M,Z){
  seq(M+Z)
}
outerfun(x=3, innerfun2,Z=3)
[1]  3  6  9 12 15 18

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