digitalmars.D - about "with statement"

khurshid (7/7) Jun 09 2013 D language have like Pascal/Delphi "with statement", which very

Jonathan M Davis (7/14) Jun 09 2013 I'm not aware of any problems with it, but there's also rarely any reaso...

mike james (1/22) Jun 09 2013
mike james (4/25) Jun 09 2013 Even Wirth gave up on the "with" statement in his later languages

bearophile (8/10) Jun 09 2013 I think he was trying to remove all the not essential features

deadalnix (5/26) Jun 09 2013 switch(foobar) with(FoobarEnum) {

Nick Sabalausky (5/11) Jun 09 2013 Oooh! That's a good one! I don't think I've ever used "with" in any
=?UTF-8?B?QWxpIMOHZWhyZWxp?= (13/20) Jun 09 2013 +1. A friend of mine is "still experimenting" with 'with' and I hate

Maxim Fomin (43/59) Jun 09 2013 import std.stdio;
Marco Leise (8/17) Jun 10 2013 Pun intended?

=?UTF-8?B?QWxpIMOHZWhyZWxp?= (3/10) Jun 10 2013 Ha ha! :) No, I missed that one.

Jacob Carlborg (4/8) Jun 10 2013 I agree, that's basically the only case I've used "with" for.
Steven Schveighoffer (6/29) Jun 10 2013 This is gold plated.

bearophile (30/34) Jun 09 2013 It's a quite useful statement, especially with enumerations or

Andrej Mitrovic (20/27) Jun 09 2013 Yep, I use this idiom a lot. It's also very useful in unittests, to

Ivan Kazmenko (6/8) Jun 09 2013 Currently, "with" does not look into "alias this" members which

khurshid (13/23) Jun 09 2013 It's very good example!!

Idan Arye (3/29) Jun 09 2013 Not very useful, as the scope of `b` and `s` is limited to

Denis Shelomovskij (7/12) Jun 10 2013 Note, that for now you can't instantiate templates in with statement,
Anthony Goins (7/14) Jun 10 2013 Am I the only one that found this useful?

Nick Sabalausky (3/11) Jun 10 2013 Ooh, that's another good one!

Baz (19/26) Jun 10 2013 You're right but the with statment in Pascal/Delphi is

"khurshid" <khurshod.normuradov gmail.com> writes:

D language have like Pascal/Delphi  "with statement",  which very 
useful for writing readable code.

http://dlang.org/statement.html#WithStatement

Maybe I'm wrong, but, I never saw  where using this statement in 
phobos  source codes, what problem using this statement?

Regards,
Khurshid.

Jun 09 2013

Jonathan M Davis <jmdavisProg gmx.com> writes:

On Sunday, June 09, 2013 12:11:23 khurshid wrote:
 D language have like Pascal/Delphi  "with statement",  which very
 useful for writing readable code.
 
 http://dlang.org/statement.html#WithStatement
 
 Maybe I'm wrong, but, I never saw  where using this statement in
 phobos  source codes, what problem using this statement?

I'm not aware of any problems with it, but there's also rarely any reason to 
use it. In most cases, it doesn't really add anything to the code, and I'd 
argue that it would make code harder to read, because it hides where the 
variables are coming from. I don't think that we'd really lose anything if we 
didn't have it, but it's there if you want to use it, and it's not going away.

- Jonathan M Davis

Jun 09 2013

"mike james" <foo bar.com> writes:

On Sunday, 9 June 2013 at 10:22:22 UTC, Jonathan M Davis wrote:
 On Sunday, June 09, 2013 12:11:23 khurshid wrote:
 D language have like Pascal/Delphi  "with statement",  which 
 very
 useful for writing readable code.
 
 http://dlang.org/statement.html#WithStatement
 
 Maybe I'm wrong, but, I never saw  where using this statement 
 in
 phobos  source codes, what problem using this statement?

 I'm not aware of any problems with it, but there's also rarely 
 any reason to
 use it. In most cases, it doesn't really add anything to the 
 code, and I'd
 argue that it would make code harder to read, because it hides 
 where the
 variables are coming from. I don't think that we'd really lose 
 anything if we
 didn't have it, but it's there if you want to use it, and it's 
 not going away.

 - Jonathan M Davis

Jun 09 2013

"mike james" <foo bar.com> writes:

On Sunday, 9 June 2013 at 10:22:22 UTC, Jonathan M Davis wrote:
 On Sunday, June 09, 2013 12:11:23 khurshid wrote:
 D language have like Pascal/Delphi  "with statement",  which 
 very
 useful for writing readable code.
 
 http://dlang.org/statement.html#WithStatement
 
 Maybe I'm wrong, but, I never saw  where using this statement 
 in
 phobos  source codes, what problem using this statement?

 I'm not aware of any problems with it, but there's also rarely 
 any reason to
 use it. In most cases, it doesn't really add anything to the 
 code, and I'd
 argue that it would make code harder to read, because it hides 
 where the
 variables are coming from. I don't think that we'd really lose 
 anything if we
 didn't have it, but it's there if you want to use it, and it's 
 not going away.

 - Jonathan M Davis

Even Wirth gave up on the "with" statement in his later languages 
design.

-<mike>-

Jun 09 2013

"bearophile" <bearophileHUGS lycos.com> writes:

mike james:

 Even Wirth gave up on the "with" statement in his later 
 languages design.

I think he was trying to remove all the not essential features 
from the design of its language, to produce something essential. 
I prefer a language that has more handy things, even if they are 
not strictly essential. Today we are still using ObjectPascal 
(FreePascal) while Oberon and the like are uncommon.

Bye,
bearophile

Jun 09 2013

"deadalnix" <deadalnix gmail.com> writes:

On Sunday, 9 June 2013 at 10:22:22 UTC, Jonathan M Davis wrote:
 On Sunday, June 09, 2013 12:11:23 khurshid wrote:
 D language have like Pascal/Delphi  "with statement",  which 
 very
 useful for writing readable code.
 
 http://dlang.org/statement.html#WithStatement
 
 Maybe I'm wrong, but, I never saw  where using this statement 
 in
 phobos  source codes, what problem using this statement?

 I'm not aware of any problems with it, but there's also rarely 
 any reason to
 use it. In most cases, it doesn't really add anything to the 
 code, and I'd
 argue that it would make code harder to read, because it hides 
 where the
 variables are coming from. I don't think that we'd really lose 
 anything if we
 didn't have it, but it's there if you want to use it, and it's 
 not going away.

 - Jonathan M Davis

switch(foobar) with(FoobarEnum) {
     // ...
}

That is golden !

Jun 09 2013

Nick Sabalausky <SeeWebsiteToContactMe semitwist.com> writes:

On Sun, 09 Jun 2013 20:09:31 +0200
"deadalnix" <deadalnix gmail.com> wrote:
 
 switch(foobar) with(FoobarEnum) {
      // ...
 }
 
 That is golden !

Oooh! That's a good one! I don't think I've ever used "with" in any
language before (never saw much point), but I probably will start using
that.

Jun 09 2013

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 06/09/2013 11:09 AM, deadalnix wrote:

 On Sunday, 9 June 2013 at 10:22:22 UTC, Jonathan M Davis wrote:

 I'd argue that it would make code harder to read, because it hides where
 the variables are coming from.


+1. A friend of mine is "still experimenting" with 'with' and I hate 
reading his code. :)

with (new C()) {
     i = 42;    // is that a member of C?
     j = 43;    // how about that?
     foo();     // and that?
     bar();     // and that?
}

Thanks for obfuscating! :)

 switch(foobar) with(FoobarEnum) {
      // ...
 }

 That is golden !

+1000 :o)

To me, 'with' is useful only in that case.

Ali

Jun 09 2013

"Maxim Fomin" <maxim maxim-fomin.ru> writes:

On Sunday, 9 June 2013 at 23:48:39 UTC, Ali Çehreli wrote:
 On 06/09/2013 11:09 AM, deadalnix wrote:

 On Sunday, 9 June 2013 at 10:22:22 UTC, Jonathan M Davis

 wrote:

 I'd argue that it would make code harder to read, because it


 hides where
 the variables are coming from.


 +1. A friend of mine is "still experimenting" with 'with' and I 
 hate reading his code. :)

 with (new C()) {
     i = 42;    // is that a member of C?
     j = 43;    // how about that?
     foo();     // and that?
     bar();     // and that?
 }

 Thanks for obfuscating! :)


 Ali

import std.stdio;

int foo()
{
    writeln("foo");
    return 0;
}

void main()
{
    short i;
    try  switch (i)
    {
       writeln(i);
       default:
          writeln("default 1");
          throw new Exception("");
    }
    catch(Exception e)  do switch(foo())
    {
       default:
          writeln("default 2");
    } while(false);
    finally if (i) switch(i) { writeln("do"); default: }
    else {}
}

One bug with this funny stuff sharing common scoped statement is

import std.stdio;

bool foo()
{
    writeln("foo");
    return true;
}

void main()
{
    short i;
    switch(i) if (foo())
    {
       default:
    }
    else
       foo();
}

It seems that if statement even doesn't reach backend.

Jun 09 2013

Marco Leise <Marco.Leise gmx.de> writes:

Am Sun, 09 Jun 2013 16:48:39 -0700
schrieb Ali =C3=87ehreli <acehreli yahoo.com>:

  > switch(foobar) with(FoobarEnum) {
  >      // ...
  > }
  >
  > That is golden !
=20
 +1000 :o)
=20
 To me, 'with' is useful only in that _case_.

Pun intended?

I even remember someone being surprised that it had other uses
than this one, but I couldn't find the post.

switch(foobar : FoobarEnum) {} ? :p

--=20
Marco

Jun 10 2013

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 06/10/2013 02:43 AM, Marco Leise wrote:

 Am Sun, 09 Jun 2013 16:48:39 -0700
 schrieb Ali Çehreli <acehreli yahoo.com>:

   > switch(foobar) with(FoobarEnum) {
   >      // ...
   > }


 To me, 'with' is useful only in that _case_.

 Pun intended?

Ha ha! :) No, I missed that one.

Ali

Jun 10 2013

Jacob Carlborg <doob me.com> writes:

On 2013-06-09 20:09, deadalnix wrote:

 switch(foobar) with(FoobarEnum) {
      // ...
 }

 That is golden !

I agree, that's basically the only case I've used "with" for.

-- 
/Jacob Carlborg

Jun 10 2013

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Sun, 09 Jun 2013 14:09:31 -0400, deadalnix <deadalnix gmail.com> wrote:

 On Sunday, 9 June 2013 at 10:22:22 UTC, Jonathan M Davis wrote:
 On Sunday, June 09, 2013 12:11:23 khurshid wrote:
 D language have like Pascal/Delphi  "with statement",  which very
 useful for writing readable code.
  http://dlang.org/statement.html#WithStatement
  Maybe I'm wrong, but, I never saw  where using this statement in
 phobos  source codes, what problem using this statement?

 I'm not aware of any problems with it, but there's also rarely any  
 reason to
 use it. In most cases, it doesn't really add anything to the code, and  
 I'd
 argue that it would make code harder to read, because it hides where the
 variables are coming from. I don't think that we'd really lose anything  
 if we
 didn't have it, but it's there if you want to use it, and it's not  
 going away.

 - Jonathan M Davis

 switch(foobar) with(FoobarEnum) {
      // ...
 }

 That is golden !

This is gold plated.

Assuming typeof(foobar) == FoobarEnum, any place FoobarEnum is expected,  
you should not have to specify FoobarEnum.

The above should not be necessary.

-Steve

Jun 10 2013

"bearophile" <bearophileHUGS lycos.com> writes:

khurshid:

 D language have like Pascal/Delphi  "with statement",  which 
 very useful for writing readable code.

It's a quite useful statement, especially with enumerations or 
associative array literals, to avoid repeating many times their 
name:

switch (en) with (MyEnum) {
   case foo: ...
   case bar: ...
}

int[MyEnum] myAA;
with (MyEnum) {
   myAA = [foo: ...,
           bar: ...,
          ];
}

Instead of:

switch (en) {
   case MyEnum.foo: ...
   case MyEnum.bar: ...
}

int[MyEnum] myAA = [
   MyEnum.foo: ...,
   MyEnum.bar: ...,
];

And D with is better than Pascal one, because it removes its main 
pitfall.


 Maybe I'm wrong, but, I never saw  where using this statement 
 in phobos  source codes, what problem using this statement?

I think it's not used much in Phobos because it's a statement not 
present in C/C++, and D/Phobos devs are more used to C/C++ 
languages than to Pascal/Ada ones.

Bye,
bearophile

Jun 09 2013

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 6/9/13, bearophile <bearophileHUGS lycos.com> wrote:
 It's a quite useful statement, especially with enumerations or
 associative array literals, to avoid repeating many times their
 name:

 switch (en) with (MyEnum) {
    case foo: ...
    case bar: ...
 }

Yep, I use this idiom a lot. It's also very useful in unittests, to
avoid copy-pasting code and polluting the namespace. A contrived
example:

-----
class C
{
    int x, y;
    this() { x = 1; y = 2; }
}

unittest
{
    with (new C)
    {
        assert(x == 1);
        assert(y == 2);
    }
}
-----

There are some bugs with it currently, but I think they're fixable.

Jun 09 2013

"Ivan Kazmenko" <gassa mail.ru> writes:

On Sunday, 9 June 2013 at 11:56:42 UTC, Andrej Mitrovic wrote:
 There are some bugs with it currently, but I think they're 
 fixable.

Currently, "with" does not look into "alias this" members which 
somewhat limits its usefulness:

http://d.puremagic.com/issues/show_bug.cgi?id=6711
http://d.puremagic.com/issues/show_bug.cgi?id=9807
(duplicates?)

Jun 09 2013

"khurshid" <khurshod.normuradov gmail.com> writes:

On Sunday, 9 June 2013 at 11:11:47 UTC, bearophile wrote:
 khurshid:

 D language have like Pascal/Delphi  "with statement",  which 
 very useful for writing readable code.

 It's a quite useful statement, especially with enumerations or 
 associative array literals, to avoid repeating many times their 
 name:

 switch (en) with (MyEnum) {
   case foo: ...
   case bar: ...
 }

It's very good example!!

And, May be, this is'not bad, too :))

struct C
{
    alias byte  B;
    alias short S;
};

with(C)
{
    B b;
    S s;
}

Jun 09 2013

"Idan Arye" <GenericNPC gmail.com> writes:

On Sunday, 9 June 2013 at 19:03:12 UTC, khurshid wrote:
 On Sunday, 9 June 2013 at 11:11:47 UTC, bearophile wrote:
 khurshid:

 D language have like Pascal/Delphi  "with statement",  which 
 very useful for writing readable code.

 It's a quite useful statement, especially with enumerations or 
 associative array literals, to avoid repeating many times 
 their name:

 switch (en) with (MyEnum) {
  case foo: ...
  case bar: ...
 }

 It's very good example!!

 And, May be, this is'not bad, too :))

 struct C
 {
    alias byte  B;
    alias short S;
 };

 with(C)
 {
    B b;
    S s;
 }

Not very useful, as the scope of `b` and `s` is limited to 
`with`'s block...

Jun 09 2013

Denis Shelomovskij <verylonglogin.reg gmail.com> writes:

09.06.2013 14:11, khurshid пишет:
 D language have like Pascal/Delphi  "with statement",  which very useful
 for writing readable code.

 http://dlang.org/statement.html#WithStatement

 Maybe I'm wrong, but, I never saw  where using this statement in phobos
 source codes, what problem using this statement?

Note, that for now you can't instantiate templates in with statement, 
see Issue 6196 [1].

[1] http://d.puremagic.com/issues/show_bug.cgi?id=6196

-- 
Денис В. Шеломовский
Denis V. Shelomovskij

Jun 10 2013

"Anthony Goins" <neontotem gmail.com> writes:

On Sunday, 9 June 2013 at 10:11:25 UTC, khurshid wrote:
 D language have like Pascal/Delphi  "with statement",  which 
 very useful for writing readable code.

 http://dlang.org/statement.html#WithStatement

 Maybe I'm wrong, but, I never saw  where using this statement 
 in phobos  source codes, what problem using this statement?

 Regards,
 Khurshid.

Am I the only one that found this useful?
Is there a better way?

with (specificModule)
{
     result = ufcsChain.ambiguousFunction.link3();
}

Jun 10 2013

Nick Sabalausky <SeeWebsiteToContactMe semitwist.com> writes:

On Mon, 10 Jun 2013 15:33:44 +0200
"Anthony Goins" <neontotem gmail.com> wrote:
 
 Am I the only one that found this useful?
 Is there a better way?
 
 with (specificModule)
 {
      result = ufcsChain.ambiguousFunction.link3();
 }

Ooh, that's another good one!

Jun 10 2013

"Baz" <Burg.Basile yahoo.com> writes:

On Sunday, 9 June 2013 at 10:11:25 UTC, khurshid wrote:
 D language have like Pascal/Delphi  "with statement",  which 
 very useful for writing readable code.

 http://dlang.org/statement.html#WithStatement

 Maybe I'm wrong, but, I never saw  where using this statement 
 in phobos  source codes, what problem using this statement?

 Regards,
 Khurshid.

You're right but the with statment in Pascal/Delphi is 
deprecated. While it was usefull in a simple branch, it was 
error-prone. In "D" the scope() statement can be used to overcome 
the old Pascal pattern: with whatIcreate try finally free.

quote from Delphi XE4 release (technical pdf):
"4. OTHER LANGUAGE CHANGES
Besides string type changes and objects memory management, there 
are other current or
expected changes in the new Delphi ARM compiler that you can 
easily start to adopt:
  Sooner or later, the with statement is going to be deprecated 
and removed from the
Delphi language. You can easily start removing it now from your 
code, and most Delphi
developer will agree this is a good idea anyway, given some of 
the hidden pitfalls of this
keyword.
"

Jun 10 2013

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