R : define a function within a function

Question

(关于R语言)

我试图在另一个函数中声明/定义一个函数。它似乎不起作用。我不认为这完全是一个错误，它可能是预期的行为，但我想了解原因!任何链接到相关手册页的答案也非常受欢迎。

谢谢

代码:

fun1 <- function(){
  print("hello")
  fun2 <- function(){ #will hopefully define fun2 when fun1 is called
    print(" world")
  }
}

fun1() #so I expected fun2 to be defined after running this line
fun2() #aaand... turns out it isn't

执行:

> fun1 <- function(){
+   print("hello")
+   fun2 <- function(){ #will hopefully define fun2 when fun1 is called
+     print(" world")
+   }
+ }
> 
> fun1() #so I expected fun2 to be defined after running this line
[1] "hello"
> fun2() #aaand... turns out it isn't
Error : could not find function "fun2"

Answer 1

如果“fun1”返回您分配给“fun2”的函数的另一种方式:

> fun1 <- function(){
+   print("hello")
+   # return a function
+   function(){ # function to be returned
+     print(" world")
+   }
+ }
> fun2 <- fun1()  # assign returned function to 'fun2'
[1] "hello"
> fun2()
[1] " world"