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July 25, 2012
[Issue 8432] New: write needs to print full enum type
http://d.puremagic.com/issues/show_bug.cgi?id=8432

          Summary: write needs to print full enum type
          Product: D
          Version: D2
         Platform: All
       OS/Version: All
           Status: NEW
         Severity: enhancement
         Priority: P2
        Component: Phobos
       AssignedTo: nobody@puremagic.com
       ReportedBy: andrej.mitrovich@gmail.com


--- Comment #0 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2012-07-25 06:20:45 PDT ---
enum X { Val }

void main()
{
   string[X] hash;
   hash[X.Val] = "1";
   writeln(hash);

   X[string] hash2;
   hash2["foo"] = X.Val;
   writeln(hash2);
}

Output:
[Val:"1"]
["foo":Val]

This should really be:
[X.Val:"1"]
["foo":X.Val]

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July 25, 2012
[Issue 8432] write needs to print full enum type
http://d.puremagic.com/issues/show_bug.cgi?id=8432


bearophile_hugs@eml.cc changed:

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


--- Comment #1 from bearophile_hugs@eml.cc 2012-07-25 07:06:16 PDT ---
There is a tradeoff here, in some situations what you ask for is good because
it makes the output more qualified and explicit:

import std.stdio;
enum FirstEnum { foo, bae }
enum SecondEnum { foo, spam }
void main() {
   auto a = FirstEnum.foo;
   auto b = SecondEnum.foo;
   writeln(a, " ", b);
}

It prints:

foo foo

While with your proposal it prints an output that allows you to see the types:

FirstEnum.foo SecondEnum.foo


But in some other cases it's not so good. In most real cases enums have a name
longer than your "X". With DMD 2.2060beta this program:


import std.stdio;
enum SomeLongEnumName { foo, bar, baz, spam }
void main() {
   SomeLongEnumName[] a;
   with (SomeLongEnumName)
        a = [foo, bar, baz, spam, foo, bar, baz, spam, foo, bar, baz, spam];
   writeln(a);
}


Prints:

[foo, bar, baz, spam, foo, bar, baz, spam, foo, bar, baz, spam]

With your proposal it prints:

[SomeLongEnumName.foo, SomeLongEnumName.bar, SomeLongEnumName.baz,
SomeLongEnumName.spam, SomeLongEnumName.foo, SomeLongEnumName.bar,
SomeLongEnumName.baz, SomeLongEnumName.spam, SomeLongEnumName.foo,
SomeLongEnumName.bar, SomeLongEnumName.baz, SomeLongEnumName.spam]

That in my opinion is unacceptably noisy.


And when you really need the enum names it's not too much hard to add them to
the textual output (despite it requires a little longer code):

import std.stdio;
enum FirstEnum { foo, bae }
enum SecondEnum { foo, spam }
void main() {
   auto a = FirstEnum.foo;
   auto b = SecondEnum.foo;
   writeln(typeof(a).stringof, ".", a, " ",
           typeof(b).stringof, ".", b);
}


It prints:

FirstEnum.foo SecondEnum.foo


An alternative idea is to print single enums qualified with their enum name and
print enums in collections without their enum name. This means this program:


import std.stdio;
enum SomeLongEnumName { foo, bar, baz, spam }
void main() {
   SomeLongEnumName a;
   SomeLongEnumName[] b;
   with (SomeLongEnumName) {
       a = bar;
       b = [foo, bar, baz, spam, foo, bar, baz, spam, foo, bar, baz, spam];
    }
   writeln(a);
   writeln(b);
}


will print:

SomeLongEnumName.bar
[foo, bar, baz, spam, foo, bar, baz, spam, foo, bar, baz, spam]

But if you want to print many single enum variables without their enum name,
how do you remove it? Adding "typeof(a).stringof, "."," before them in the
writeln is simpler than removing the lading enum name. Python2 print statement
adds a space between items, this is usually handy, but when you don't want that
damned space, you have to use other functions from the std.library. This was so
bad that in Python3 they have fixed it. Generally adding is simpler than
removing.

So in the end I am against your proposal, and I think the current situation is
the best of all the alternatives I can think of (but maybe someone is able to
find a better new idea).

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July 25, 2012
[Issue 8432] write needs to print full enum type
http://d.puremagic.com/issues/show_bug.cgi?id=8432



--- Comment #2 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2012-07-25 09:02:56 PDT ---
If you use enum arrays with writeln() you would typically use shorter names. My
issue is that this can make reading output ambiguous:

enum X { foo }
enum Y { foo }

void main()
{
   X x;
   Y y;
   writeln(x);
   writeln(y);
}

outputs:
foo
foo

In C++ you don't have to use the enum tag, but in D you do, and it would make
sense to output the correct type definition.

Consider another case which is why I filed this:

enum Type { Class, Struct, Enum }

struct Class { }
struct Struct { }
struct Enum { }

void main()
{
   Type[string] type = ["foo" : Type.Class];
   writeln(type);
}

outputs:
["foo":Class]

This output confused me since Class is both a struct definition and a named
enumerated value. I use writeln() almost strictly for debugging and I would
really want to see *valid* type info, which means a string representation that
could be re-inserted into code which you could practically mix in (not that I
would do that but it makes sense to keep a 1:1 mapping like this).

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[Issue 8432] write needs to print full enum type
http://d.puremagic.com/issues/show_bug.cgi?id=8432



--- Comment #3 from bearophile_hugs@eml.cc 2012-07-25 11:54:03 PDT ---
(In reply to comment #2)

> enum Type { Class, Struct, Enum }
> 
> struct Class { }
> struct Struct { }
> struct Enum { }
> 
> void main()
> {
>     Type[string] type = ["foo" : Type.Class];
>     writeln(type);
> }
> 
> outputs:
> ["foo":Class]
> 
> This output confused me since Class is both a struct definition and a named
> enumerated value.

A partial solution is to add the type:

writeln(typeof(type).stringof, ": ", type);

It prints:

Type[string]: ["foo":Class]

Now you see that the keys can't be the struct name.

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January 27, 2013
[Issue 8432] format should qualify enum type with its value
http://d.puremagic.com/issues/show_bug.cgi?id=8432


Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
        AssignedTo|nobody@puremagic.com        |andrej.mitrovich@gmail.com
           Summary|write needs to print full   |format should qualify enum
                  |enum type                   |type with its value


--- Comment #4 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-01-26 16:41:39 PST ---
Other than introducing a new format specifier, I'm not sure how to proceed.

Perhaps a '%q' for "qualified" would do it.

Andrei if you're reading this I'd like to get an opinion so I can work on it or
close the report. Thanks.

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February 03, 2013
[Issue 8432] format should qualify enum type with its value
http://d.puremagic.com/issues/show_bug.cgi?id=8432


Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
            Status|NEW                         |RESOLVED
        Resolution|                            |WONTFIX


--- Comment #5 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-02-03 13:01:48 PST ---
Not too important for me, I'm closing it.

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