R help - Oct 2022 - unexpected 'else' in " else"

Richard O'Keefe's remarks on the workings of the interpreter are
correct, but the code examples are ugly and hard to read. (On the other hand,
anyone who has used the debugger may be de-sensitised to horrible code
formatting.) The use of whitespace should if possible reflect the structure of
the code, and I would usually rather throw in a few extra delimiters than
obscure the structure.

Regards,
Jorgen Harmse.


Examples (best viewed in a real text editor so things line up):


{ if (x<y)
    z <- x
  else
    z <- y
}

Or

{ if(x<y) z <- x
  else z <- y
}

x <- ( y
      + z)

Or

( x
<- y
   + z
)

Or

?


Message: 1
Date: Wed, 26 Oct 2022 23:03:30 +1300
From: "Richard O'Keefe" <raoknz at gmail.com>
To: Jinsong Zhao <jszhao at yeah.net>
Cc: "r-help at r-project.org" <r-help at r-project.org>
Subject: Re: [R] unexpected 'else' in " else"
Message-ID:
        <CABcYAd+=v6FvOqi7JjK7iR5RScVdDBGZK_BASQ-z0=k6TKEyYA at
mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

...

The basic issue is that the top level wants to get started
on your command AS SOON AS IT HAS A COMPLETE COMMAND,
and if (...) stmt
is complete.  It's not going to hang around "Waiting for Godot"
for an 'else' that might never ever ever turn up.  So
   if (x < y) z <-
   x else z <- y
is absolutely fine, no braces needed, while
   if (x < y) z <- x
   else z <- y
will see the eager top level rush off to do your bidding
at the end of the first line and then be completely
baffled by an 'else' where it does not expect one.

It's the same reason that you break AFTER infix operators
instead of BEFORE.
   x <- y +
   z
works fine, while
   x <- y
   + z
doesn't.





	[[alternative HTML version deleted]]

I appreciate this thread on coding. My preference for reading is to have
complete sentences.
I can read this:
{ if (x<y)
    z <- x
  else
    z <- y
}

This is much harder no matter how nicely everything is lined up.
{ if 
    (x<
     y)
       z <- 
       x
  else
       z <- 
       y
}


Regards,
Tim

-----Original Message-----
From: R-help <r-help-bounces at r-project.org> On Behalf Of Jorgen Harmse
via R-help
Sent: Friday, October 28, 2022 10:39 AM
To: r-help at r-project.org
Subject: Re: [R] unexpected 'else' in " else"

[External Email]

Richard O'Keefe's remarks on the workings of the interpreter are
correct, but the code examples are ugly and hard to read. (On the other hand,
anyone who has used the debugger may be de-sensitised to horrible code
formatting.) The use of whitespace should if possible reflect the structure of
the code, and I would usually rather throw in a few extra delimiters than
obscure the structure.

Regards,
Jorgen Harmse.


Examples (best viewed in a real text editor so things line up):


{ if (x<y)
    z <- x
  else
    z <- y
}

Or

{ if(x<y) z <- x
  else z <- y
}

x <- ( y
      + z)

Or

( x
<- y
   + z
)

Or

 


Message: 1
Date: Wed, 26 Oct 2022 23:03:30 +1300
From: "Richard O'Keefe" <raoknz at gmail.com>
To: Jinsong Zhao <jszhao at yeah.net>
Cc: "r-help at r-project.org" <r-help at r-project.org>
Subject: Re: [R] unexpected 'else' in " else"
Message-ID:
        <CABcYAd+=v6FvOqi7JjK7iR5RScVdDBGZK_BASQ-z0=k6TKEyYA at
mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

...

The basic issue is that the top level wants to get started on your command AS
SOON AS IT HAS A COMPLETE COMMAND, and if (...) stmt is complete.  It's not
going to hang around "Waiting for Godot"
for an 'else' that might never ever ever turn up.  So
   if (x < y) z <-
   x else z <- y
is absolutely fine, no braces needed, while
   if (x < y) z <- x
   else z <- y
will see the eager top level rush off to do your bidding at the end of the first
line and then be completely baffled by an 'else' where it does not
expect one.

It's the same reason that you break AFTER infix operators instead of BEFORE.
   x <- y +
   z
works fine, while
   x <- y
   + z
doesn't.





        [[alternative HTML version deleted]]