[R] unexpected 'else' in " else"

[Jinsong Zhao]

Dear John,

Thank you very much for the explanation. It cleared up my confusion 
about the syntax of "if ... else...", which in the help page of "if" said:
```
In particular, you should not have a newline between ‘}’ and
      ‘else’ to avoid a syntax error in entering a ‘if ... else’
      construct at the keyboard or via ‘source’.
```

Best,
Jinsong


On 2022/10/21 21:49, John Fox wrote:
> Dear Jinsong,
>
> When you enter these code lines at the R command prompt, the 
> interpreter evaluates an expression when it's syntactically complete, 
> which occurs before it sees the else clause. The interpreter can't 
> read your mind and know that an else clause will be entered on the 
> next line. When the code lines are in a function, the function body is 
> enclosed in braces and so the interpreter sees the else clause.
>
> As I believe was already pointed out, you can similarly use braces at 
> the command prompt to signal incompleteness of an expression, as in
>
> > {if (FALSE) print(1)
> + else print(2)}
> [1] 2
>
> I hope this helps,
>  John
>