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digitalmars.D.bugs - [Issue 5142] New: writefln should allow no arguments (no formating string)

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5142

           Summary: writefln should allow no arguments (no formating
                    string)
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: baryluk smp.if.uj.edu.pl



06:03:52 PDT ---
In D1 it is allowed to write

  writefln();

In D2 it is no more. This problem exists for more than year now, after writefln
is actually template. Disallowing writefln without parameters (as above) makes
porting D1 software really a pain (one need to change writefln(); to
writeln()), and is inconsistant (propgramer always need to remember which
function to use, and makes edditing annoying).

Thanks.

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5142


Steven Schveighoffer <schveiguy yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |schveiguy yahoo.com
         Resolution|                            |WONTFIX



08:36:41 PDT ---
This was a deliberate change.

The benefit of writeln is that you can put formatting characters in strings
without having them interpreted as formatting sequences.

I don't think it's that big of a pain -- the compiler should tell you all the
places where you have messed up.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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10:33:21 PDT ---

 This was a deliberate change.
 
 The benefit of writeln is that you can put formatting characters in strings
 without having them interpreted as formatting sequences.


And how this resolves my problem? I was talking about writefln behaviour, not
writeln!


 I don't think it's that big of a pain -- the compiler should tell you all the
 places where you have messed up.


Yes, it is. Much simpler is just to add empty template writefln() specizliation
which will just call writeln();, for the sake of consistency, and compatibility
with old code.

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11:08:04 PDT ---


 This was a deliberate change.
 
 The benefit of writeln is that you can put formatting characters in strings
 without having them interpreted as formatting sequences.


 
 And how this resolves my problem? I was talking about writefln behaviour, not
 writeln!


writeln is for without formatting, writefln is for with formatting.  writefln
expects its first argument to be a string, if it's not a string, then you
aren't calling it properly.


 

 I don't think it's that big of a pain -- the compiler should tell you all the
 places where you have messed up.


 Yes, it is. Much simpler is just to add empty template writefln() specizliation
 which will just call writeln();, for the sake of consistency, and compatibility
 with old code.


But there is no formatting string.  It's like saying pow(2) should be
equivalent to pow(2, 1).  It makes no sense to call it.  The formatting string
is an essential parameter.

Typing writeln() instead of writefln() is hardly a 'pain', and it's a compile
time error.  Compile time errors are easy to find because the compiler points
them all out for you.  No special searching is necessary.

in fact, here is a special script I wrote in about 5 seconds which will solve
all your problems:

find . -name '*.d' -exec sed 's/writefln()/writeln()/g' {} \;

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs eml.cc






 writeln is for without formatting, writefln is for with formatting.  writefln
 expects its first argument to be a string, if it's not a string, then you
 aren't calling it properly.


I agree.

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04:16:05 PDT ---




 This was a deliberate change.
 
 The benefit of writeln is that you can put formatting characters in strings
 without having them interpreted as formatting sequences.


 
 And how this resolves my problem? I was talking about writefln behaviour, not
 writeln!


 
 writeln is for without formatting, writefln is for with formatting.  writefln
 expects its first argument to be a string, if it's not a string, then you
 aren't calling it properly.


As I written, in D1 it was correct behavior. Additionally it is unnecessary
restriction and inconsistency.

Lets see at some common type of code in C:


  printf("\n");
  printf("a=%d b=%f\n", a, b);
  printf("c=%d d=%f\n", c, d);
  printf("\n");
  printf("\n");


(slightly artificial but I have lots of such or similar printf like statements.
I also saw this frequently in others people code).

It is much cleaner and visually appealing than:

  printf("a=%d b=%f\n\n", a, b);
  printf("c=%d d=%f\n\n\n", c, d);

Because you do not see easily where are additional empty lines, and do not
immiedietly see structure of output.

In D1, one could write:

  writefln();
  writefln("a=%d b=%f", a, b);
  writefln("c=%d d=%f", c, d);
  writefln();
  writefln();


Whit is even nicer. It also simplifies reaaranging and editing arguments.

In D2, one needs to write:

  writeln();
  writefln("a=%d b=%f", a, b);
  writefln("c=%d d=%f", c, d);
  writeln();
  writeln();

Which introduces unnecessary burded to the code.

You also cannot just add parameters, like in D1. Suppose you want to add them
to this:

  writefln("c=%d d=%f", c, d);
  writeln();
  writeln();

Then you add them:

  writefln("c=%d d=%f", c, d);
  writeln("f=%f g=%d", f, g);
  writeln();



But, well, it is incorrect, you need to remember to change writeln to writefln.
D1 was simpler and cleaner.


One of potentiality possibility is to just write writefln("");. But this isn't
so common code.

Not to mention, that one can also use other usefull tricks, without formating
string: writefln("f=", f, " g=", g); but this is beyond scope of this bug
report (and I understand that writefln("s=", s, f), can not work as expected
when s="fff%fff", by pure accident). This also makes porting harder, but will
just leave it (There is almost good solution for this problem, but I understand
that it will need some exception, which isn't good as it can fool beginners).



 in fact, here is a special script I wrote in about 5 seconds which will solve
 all your problems:
 
 find . -name '*.d' -exec sed 's/writefln()/writeln()/g' {} \;


Not exactly all. What if I have aliases, or imported writefln with other
symbolic name? What if I used other style of brackets, like "writefln ( );"?
Can be resolved with some additional work, or with good IDE (which D lacks),
but why break unnecessarily compatibility (of course there will be other
problems with doing D1->D2 port, but just please make it simpler, not harder).


I have thousands of occurrences of this problems in one of the projects. And
spent about 2 hours fixing it.


...


 I agree.




I understand, but do not agree with rationale.


Thanks for your time. I know that this should be discussed on mailing list, but
was hoping it is simpler problem.

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