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September 26, 2012
[Issue 8727] New: __traits(is_reserved_word, "") ?
http://d.puremagic.com/issues/show_bug.cgi?id=8727

          Summary: __traits(is_reserved_word, "") ?
          Product: D
          Version: D2
         Platform: All
       OS/Version: All
           Status: NEW
         Severity: enhancement
         Priority: P2
        Component: DMD
       AssignedTo: nobody@puremagic.com
       ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2012-09-26 07:16:33 PDT ---
Maybe it's worth adding a new trait that tells what currently are reserved
words of D:

assert(__traits(is_reserved_word, "import"));

For an use case see:
http://d.puremagic.com/issues/show_bug.cgi?id=6946

It replaces a function like this, that risks becoming out of date:

bool isReservedWord(in string w) {
   string[] reservedWords = "abstract alias align asm
   assert auto body bool break byte case cast catch cdouble cent cfloat
   char class const continue creal dchar debug default delegate delete
   deprecated do double else enum export extern false final finally
   float for foreach foreach_reverse function goto idouble if ifloat
   immutable import in inout int interface invariant ireal is lazy long
   macro mixin module new nothrow null out override package pragma
   private protected public pure real ref return scope shared short
   static struct super switch synchronized template this throw true try
   typedef typeid typeof ubyte ucent uint ulong union unittest ushort
   version void volatile wchar while with __FILE__ __LINE__ __gshared
   __thread __traits".split();
   return canFind(reservedWords, w);
}


Such __traits is useful to exclude the reserved words from usages in code
generation, to avoid bugs or avoid mysterious error messages.

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September 26, 2012
[Issue 8727] __traits(is_reserved_word, "") ?
http://d.puremagic.com/issues/show_bug.cgi?id=8727


Alex Rønne Petersen <alex@lycus.org> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
          Keywords|                            |pull
                CC|                            |alex@lycus.org


--- Comment #1 from Alex Rønne Petersen <alex@lycus.org> 2012-09-26 17:03:16 CEST ---
https://github.com/D-Programming-Language/dmd/pull/1144

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September 26, 2012
[Issue 8727] __traits(is_reserved_word, "") ?
http://d.puremagic.com/issues/show_bug.cgi?id=8727



--- Comment #2 from bearophile_hugs@eml.cc 2012-09-26 08:30:14 PDT ---
(In reply to comment #1)
> https://github.com/D-Programming-Language/dmd/pull/1144

Thank you, only 45 minutes to see implemented one enhancement request of mine
:-)

(Regarding the comments inside your patch, "foreach_reverse" is quite useful.
retro() will be acceptable only if the compiler recognizes it as special and
guarantees to implement it with the the same efficiency of foreach_reverse in
all cases. I think this will not happen, so I'll try to keep "foreach_reverse"
inside the language.)

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[Issue 8727] __traits(is_reserved_word, "") ?
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monarchdodra@gmail.com changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
                CC|                            |monarchdodra@gmail.com


--- Comment #3 from monarchdodra@gmail.com 2012-09-26 08:52:13 PDT ---
(In reply to comment #2)
> (In reply to comment #1)
> > https://github.com/D-Programming-Language/dmd/pull/1144
> 
> Thank you, only 45 minutes to see implemented one enhancement request of mine
> :-)
> 
> (Regarding the comments inside your patch, "foreach_reverse" is quite useful.
> retro() will be acceptable only if the compiler recognizes it as special and
> guarantees to implement it with the the same efficiency of foreach_reverse in
> all cases. I think this will not happen, so I'll try to keep "foreach_reverse"
> inside the language.)

I don't want to hijack this pull request into off topic discussion, but is
foreach_reverse *really* scheduled for deprecation? Or is this just an ongoing
suggestion. If it is an ER, do you have a link to it?

IMO, The problem with retro is that it does not support natural slice syntax:

--------
import std.range;
import std.stdio;

void main()
{
   foreach_reverse(i; 0..10)
     writeln(i, "...");
   writeln("Fire!");

   foreach(i; retro(0..10)) //NOPE
     writeln(i, "...");
   writeln("Fire!");
}
--------

The equivalent code would require inserting an iota. Either from 9 to -1 (ew),
or from 0 to 10, then reversed (blargh):

--------
void main()
{
   foreach_reverse(i; 0..10)
     writeln(i, "...");
   writeln("Fire!");

   foreach(i; iota(9, -1, -1)) //Ew
     writeln(i, "...");
   writeln("Fire!");

   foreach(i; iota(0, 10).retro() ) //Blargh
     writeln(i, "...");
   writeln("Fire!");
}
--------

Looking only at the syntax, I'd like to keep foreach_reverse thankyou very
much. I also doubt that the performance is anywhere near the same level.

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September 26, 2012
[Issue 8727] __traits(is_reserved_word, "") ?
http://d.puremagic.com/issues/show_bug.cgi?id=8727


Jonathan M Davis <jmdavisProg@gmx.com> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
                CC|                            |jmdavisProg@gmx.com


--- Comment #4 from Jonathan M Davis <jmdavisProg@gmx.com> 2012-09-26 10:15:44 PDT ---
> I don't want to hijack this pull request into off topic discussion, but is
foreach_reverse *really* scheduled for deprecation?

I haven't gotten a clear answer on that. I don't think that there's much
question that if we were completely redoing things, it wouldn't be in the
language, and there's a definite contingent who want it gone. But I don't know
whether Walter intends to axe it or not. AFAIK, no definitive decision was made
on it. It's not on the list of features to be deprecated on dlang.org:

http://dlang.org/deprecate.html

There's probably a good chance that foreach_reverse will cease to work with
delegates at some point even if it's kept, because it does exactly the same
thing as foreach for delegates, making it a source of bugs. But there's
probably a good chance that foreach_reverse is here to stay simply to avoid
breaking code even if it's certain that we don't want it.

Regardless, if you want someone like Walter who would know for sure what
foreach_reverse's current fate is supposed to be, you'll probably have to post
in the newsgroup (and short of Walter or Andrei saying something, I don't know
if you can know for certain what the current situation is, since it's Walter's
decision, and I'm not aware of him making a public decision on it).

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October 10, 2012
[Issue 8727] __traits(is_reserved_word, "") ?
http://d.puremagic.com/issues/show_bug.cgi?id=8727


Alex Rønne Petersen <alex@lycus.org> changed:

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


--- Comment #5 from Alex Rønne Petersen <alex@lycus.org> 2012-10-10 02:46:53 CEST ---
OK, I think this can be implemented as a library trait.

Anyone want to send a pull request that adds it to std.traits?

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[Issue 8727] __traits(is_reserved_word, "") ?
http://d.puremagic.com/issues/show_bug.cgi?id=8727


monarchdodra@gmail.com changed:

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


--- Comment #6 from monarchdodra@gmail.com 2012-10-10 00:27:20 PDT ---
(In reply to comment #5)
> OK, I think this can be implemented as a library trait.
> 
> Anyone want to send a pull request that adds it to std.traits?

I can do it.

I'll use the list here:
https://github.com/D-Programming-Language/dmd/blob/82ebe0357511c60b3526682afd8c2209a0861c48/src/lexer.c#L2806

Re-opening.

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[Issue 8727] __traits(is_reserved_word, "") ?
http://d.puremagic.com/issues/show_bug.cgi?id=8727



--- Comment #7 from monarchdodra@gmail.com 2012-10-10 10:09:19 PDT ---
(In reply to comment #6)
> (In reply to comment #5)
> > OK, I think this can be implemented as a library trait.
> > 
> > Anyone want to send a pull request that adds it to std.traits?
> 
> I can do it.
> 
> I'll use the list here:
> https://github.com/D-Programming-Language/dmd/blob/82ebe0357511c60b3526682afd8c2209a0861c48/src/lexer.c#L2806
> 
> Re-opening.

I wrote the code, the documentation, and the unit tests. The thing though is
that I don't really care for this enhancement, and don't feel like pushing for
it. I'm dumping my work here. May someone who cares for this (bearophile?) take
over it.

//--------
/**
If $(D s) is a D reserved keyword, returns true.
*/
bool isReservedWord(in string s)
{
   //Obtained from lexer.c, and sorted
   string[] reservedWords =
   [
"__FILE__", "__LINE__", "__argTypes", "__gshared", "__overloadset",
"__parameters", "__thread", "__traits", "__vector", "abstract", "alias",
"align", "asm", "assert", "auto", "body", "bool", "break", "byte", "case",
"cast", "catch", "cdouble", "cent", "cfloat", "char", "class", "const",
"continue", "creal", "dchar", "debug", "default", "delegate", "delete",
"deprecated", "do", "double", "else", "enum", "export", "extern", "false",
"final", "finally", "float", "for", "foreach", "foreach_reverse",
"function", "goto", "idouble", "if", "ifloat", "immutable", "import", "in",
"inout", "int", "interface", "invariant", "ireal", "is", "lazy", "long",
"macro", "mixin", "module", "new", "nothrow", "null", "out", "override",
"package", "pragma", "private", "protected", "public", "pure", "real",
"ref", "return", "scope", "shared", "short", "static", "struct", "super",
"switch", "synchronized", "template", "this", "throw", "true", "try",
"typedef", "typeid", "typeof", "ubyte", "ucent", "uint", "ulong", "union",
"unittest", "ushort", "version", "void", "volatile", "wchar", "while",
"with"
   ];

   auto found = reservedWords.assumeSorted().equalRange(s);
   return !found.empty;
}

void main()
{
   //obtained from lexer.c, not sorted
   string[] words =
   [
"this", "super", "assert", "null", "true", "false", "cast", "new",
"delete", "throw", "module", "pragma", "typeof", "typeid", "template",
"void", "byte", "ubyte", "short", "ushort", "int", "uint", "long",
"ulong", "cent", "ucent", "float", "double", "real", "bool", "char",
"wchar", "dchar", "ifloat", "idouble", "ireal", "cfloat", "cdouble",
"creal", "delegate", "function", "is", "if", "else", "while", "for",
"do", "switch", "case", "default", "break", "continue", "synchronized",
"return", "goto", "try", "catch", "finally", "with", "asm", "foreach",
"foreach_reverse", "scope", "struct", "class", "interface", "union",
"enum", "import", "mixin", "static", "final", "const", "typedef",
"alias", "override", "abstract", "volatile", "debug", "deprecated",
"in", "out", "inout", "lazy", "auto", "align", "extern", "private",
"package", "protected", "public", "export", "body", "invariant",
"unittest", "version", "__argTypes", "__parameters", "ref", "macro",
"pure", "nothrow", "__thread", "__gshared", "__traits", "__vector",
"__overloadset", "__FILE__", "__LINE__", "shared", "immutable"
   ];
   foreach(ss; words)
       assert(isReservedWord(ss));
   assert(!isReservedWord("foo"));
   //CTFE:
   static assert(isReservedWord("this"));
   static assert(!isReservedWord("bar"));
}
//--------

So yeah, not assigned to me anymore :(

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October 12, 2012
[Issue 8727] __traits(is_reserved_word, "") ?
http://d.puremagic.com/issues/show_bug.cgi?id=8727



--- Comment #8 from bearophile_hugs@eml.cc 2012-10-12 14:24:14 PDT ---
(In reply to comment #7)

> bool isReservedWord(in string s)
> {
>     //Obtained from lexer.c, and sorted
>     string[] reservedWords =
>     [
> "__FILE__", "__LINE__", "__argTypes", "__gshared", "__overloadset",
...

The problem with putting a list of words like this in Phobos is that if a new
keyword is added, this function breaks. So it's better for this function to be
built inside __traits() and to use the list of keywords used by the compiler
itself.

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[Issue 8727] __traits(is_reserved_word, "") ?
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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
                CC|                            |andrej.mitrovich@gmail.com


--- Comment #9 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-01-10 11:23:57 PST ---
(In reply to comment #7)
> I wrote the code, the documentation, and the unit tests. The thing though is
> that I don't really care for this enhancement, and don't feel like pushing for
> it.

This is actually very useful for generic code, it allows one to generate
identifiers while ensuring they don't conflict with keywords.

It's also useful in code generators written in D, which can use this function
to generate C/C++ wrappers code which doesn't conflict with D keywords.

I'd say make it a pull, it's your work after all. :)

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