Does the line break between "}" and "else" really matters?-CodePudding

It is clearly that the documentation of R clearly goes against having a break line between "}" and "else". However, it is odd that the first piece of codes works but the second one does not work (syntax error)

First program

x = 1

stupid_function = function(x){
  if(x != 1){
    print("haha")
  } 
  else if( x == 1){
    print("hihi")
  }
}

stupid_function(x)
[1] "hihi"

Second program

x = 1

if(x != 1){
  print("haha")
} 
else if( x == 1){
  print("hihi")
}



Error in source("~/.active-rstudio-document", echo = TRUE) : 
    ~/.active-rstudio-document:6:3: unexpected 'else'
    5:   } 
    6:   else

CodePudding user response：

In the second program it sees a line at a time as it is typed in so at the point that the line with the } is typed in it cannot know that there will be further lines with an else so it assumes the statement is finished.

In the first case it can see all the code before it is run because it can see all the code in the function so it knows that the } has not finished the statement.

This line of argument works for an if/else but does not work in general. For example, this will produce an error when the function is defined.

f <- function(x) {
  x 
  * 2
}

CodePudding user response：

Note that the if else need not be in a function for it to work. It just need to be in a continuous form or in a way to be expressed as a continuous block of code. One way is being in a function. The other is to write it in one line, or even ensure that there is no line break between the if block and the else block:

x <- 1
if(x != 1) print('haha') else print('hihi')
[1] "hihi"

More blocks of statements:

x <- 1
if(x != 1){
  print("haha")
} else if( x == 1){ # Note how else begins immediatley after }
  print("hihi")
}

[1] "hihi"

Note that you need to know when to put the line breaks whether in a function or outside of a function. Otherwise the code might fail or even give incorrect results.

Using subtraction:

 x <- 1
 x - 
 2
 [1] -1

 x <- 1
 x
 - 2
 [1] -2

You need to know when/where to have the line breaks. Its always safe to have else follow the closing brace } of the previous if statement. ie:

  if(...){
    ....
  } else if(...){
    ....
  } else {
   ...
  }