[nem-bug] [Nemerle 0000724]: if/else & return values

[feedback at nemerle.org]

A NOTE has been added to this issue.
======================================================================
<http://nemerle.org/bugs/view.php?id=724> 
======================================================================
Reported By:                IT
Assigned To:                
======================================================================
Project:                    Nemerle
Issue ID:                   724
Category:                   The Macro Library
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
======================================================================
Date Submitted:             07-31-2006 08:51 CEST
Last Modified:              08-02-2006 15:58 CEST
======================================================================
Summary:                    if/else & return values
Description: 
This code gives me an error:

def foo() : int
{
  if (1 > 2)
  {
    _ = 1;
  }
  else
    3
  4
}

_ = foo();

======================================================================

----------------------------------------------------------------------
 Snaury - 07-31-06 09:39 
----------------------------------------------------------------------
I don't see any bug here. First, you should have written it like this:

def foo() : int
{
  if (1 > 2)
  {
    _ = 1;
  }
  else
    3;
  4
}

But then you'd get different values (void and int) in different branches
of int, so it really should have been:

def foo() : int
{
  if (1 > 2)
  {
    _ = 1;
  }
  else
    _ = 3;
  4
}

----------------------------------------------------------------------
 VladD2 - 07-31-06 23:10 
----------------------------------------------------------------------
I agree with Snaury.

----------------------------------------------------------------------
 IT - 08-01-06 03:21 
----------------------------------------------------------------------
Got it. If/else is more an operator than a statement. But it's confusing at
least for beginning.

This issue needs to be closed.

----------------------------------------------------------------------
 VladD2 - 08-01-06 21:39 
----------------------------------------------------------------------
Nemerle has no statement. And it's cool! :)

----------------------------------------------------------------------
 IT - 08-02-06 05:23 
----------------------------------------------------------------------
In this particular case it's not cool, it's confusing. I did not expect two
different branches of code to return values of the same type. I did not
even mean the 'if' part to return anything.

Well, I understand I am talking as an imperative style developer. So, I
want to try and to see if this feature is not going to get annoying when I
get inspired :)

----------------------------------------------------------------------
 Snaury - 08-02-06 10:03 
----------------------------------------------------------------------
If you want imperative style statements you can always use
Nemerle.Imperative. Just don't forget to ignore unneeded return values
(with _ = ...) and use regular break/continue/return like in other
languages. But in your example for this bug it was more of a forgotten
semicolon, btw. :)

using Nemerle.Imperative;

def foo() : int
{
  if(1 > 2)
    _ = 1
  else
    return 3;
  return 4; // or just `4'
}

But honestly, once you understand that (almost) everything in Nemerle are
expressions, you will be able to do things you couldn't even imagine to do
in other languages. :) At lease so was for me...



----------------------------------------------------------------------
 aleksey - 08-02-06 15:52 
----------------------------------------------------------------------
"Code blocks" might be viable alternative for return and break.

def foo() : int
{
  ret : {
    if (1 > 2)
      _ = 1;
    else
      ret(3);
    4
  }
}

I dunno why, but more code I write in Nemerle more do I prefer its
"indentation-based" syntax over curly-braced one. Seemingly code blocks
look much better in identation-based syntax too.

def foo() : int
  ret : 
    if (1 > 2)
      _ = 1
    else
      ret(3)
    4

----------------------------------------------------------------------
 Snaury - 08-02-06 15:58 
----------------------------------------------------------------------
About indentation syntax, me too. :) Sadly current nemerle for emacs seems
to be buggy, so whenever I press Ctrl+Alt+\ it would just turn my
indentation into trash...

Issue History
Date Modified  Username       Field                    Change              
======================================================================
07-31-06 08:51 IT             New Issue                                    
07-31-06 09:39 Snaury         Note Added: 0001383                          
07-31-06 23:10 VladD2         Note Added: 0001384                          
08-01-06 03:21 IT             Note Added: 0001385                          
08-01-06 21:39 VladD2         Note Added: 0001388                          
08-02-06 05:23 IT             Note Added: 0001389                          
08-02-06 10:02 Snaury         Note Added: 0001390                          
08-02-06 10:03 Snaury         Note Edited: 0001390                         
08-02-06 15:52 aleksey        Note Added: 0001391                          
08-02-06 15:58 Snaury         Note Added: 0001392                          
======================================================================