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digitalmars.D - The Sweet With

reply Tomasz Sowi&#324;ski <tomeksowi wp.pl> writes:
Ideas for features based on the with.

The with can make calling functions with enum arguments sexier. So instead of:
auto d = dirEntries(".", SpanMode.breadth);

you could say:
auto d = dirEntries(".", breadth);

by declaring the function as:
dirEntries(string path, with SpanMode mode);    // "with" does the trick

At first glance, such feature seems lesser. But I noticed that for fear of
redundancy programmers resort to cluttering the global scope with constants, or
even worse - using bool to offer only two options. So when the API needs an
equivalent of GUI's dropdown list, the with encourages the right way - enums.


The with can also tidy up numerous imports:

import extremely.long.package.name.module1;
import extremely.long.package.name.module2;
import extremely.long.package.name.module3;
import renamed = extremely.long.package.name.module4;
import extremely.long.package.name.module5 : selective;
...

could be compressed to:

import with (extremely.long.package.name)
{
    module1;
    module2;
    module3;
    renamed = module4;
    module5 : selective;
    ...
}

or even:

import with (extremely.long.package.name)
    module1, module2, module3, renamed = module4, module5 : selective, ... ;


What do you say?

Tomek
Mar 03 2009
parent reply Walter Bright <newshound1 digitalmars.com> writes:
Tomasz Sowi&#324;ski wrote:
 Ideas for features based on the with.
 
 The with can make calling functions with enum arguments sexier. So instead of:
 auto d = dirEntries(".", SpanMode.breadth);
 
 you could say:
 auto d = dirEntries(".", breadth);
 
 by declaring the function as:
 dirEntries(string path, with SpanMode mode);    // "with" does the trick

It looks nice, but has a subtle and disastrous problem. In D, arguments are fully resolved *before* overloading is done. If some of the overloads have with declarations, then there's a nightmarish problem of trying to mix overloading and argument resolution together.
Mar 03 2009
next sibling parent reply Jarrett Billingsley <jarrett.billingsley gmail.com> writes:
On Tue, Mar 3, 2009 at 1:50 PM, Walter Bright
<newshound1 digitalmars.com> wrote:
 Tomasz Sowi&#324;ski wrote:
 Ideas for features based on the with.

 The with can make calling functions with enum arguments sexier. So inste=


 of:
 auto d =3D dirEntries(".", SpanMode.breadth);

 you could say:
 auto d =3D dirEntries(".", breadth);

 by declaring the function as:
 dirEntries(string path, with SpanMode mode); =A0 =A0// "with" does the t=


 It looks nice, but has a subtle and disastrous problem. In D, arguments a=

 fully resolved *before* overloading is done. If some of the overloads hav=

 with declarations, then there's a nightmarish problem of trying to mix
 overloading and argument resolution together.

What about the feature you mentioned at the D con, about being able to use enums without the enum name? Or will/would that only be for things where it's really obvious, like switch statements?
Mar 03 2009
next sibling parent "Nick Sabalausky" <a a.a> writes:
 "Jarrett Billingsley" <jarrett.billingsley gmail.com> wrote in message 
 news:mailman.901.1236111433.22690.digitalmars-d puremagic.com...
 On Tue, Mar 3, 2009 at 1:50 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:
 Tomasz Sowi&#324;ski wrote:
 Ideas for features based on the with.

 The with can make calling functions with enum arguments sexier. So 
 instead
 of:
 auto d = dirEntries(".", SpanMode.breadth);

 you could say:
 auto d = dirEntries(".", breadth);

 by declaring the function as:
 dirEntries(string path, with SpanMode mode); // "with" does the trick

It looks nice, but has a subtle and disastrous problem. In D, arguments are fully resolved *before* overloading is done. If some of the overloads have with declarations, then there's a nightmarish problem of trying to mix overloading and argument resolution together.

What about the feature you mentioned at the D con, about being able to use enums without the enum name? Or will/would that only be for things where it's really obvious, like switch statements?

Unless that was only for things like switch statements, I would hate that. I've used enums in languages that worked that way, and I found it to be such a problematic namespace-clutterer that in those languages I always hack up my enum definitions like this: enum Color { Color_Red, Color_Blue, Color_Orange, // etc... } Which is a style that I've always considered an ugly and kludgey, but unfortunately necessary, substitute for manditory enum names.
Mar 03 2009
prev sibling parent Walter Bright <newshound1 digitalmars.com> writes:
Jarrett Billingsley wrote:
 What about the feature you mentioned at the D con, about being able to
 use enums without the enum name?  Or will/would that only be for
 things where it's really obvious, like switch statements?

As I recall, only some of that would work because of this problem.
Mar 03 2009
prev sibling parent Jarrett Billingsley <jarrett.billingsley gmail.com> writes:
On Tue, Mar 3, 2009 at 3:32 PM, Nick Sabalausky <a a.a> wrote:
 "Jarrett Billingsley" <jarrett.billingsley gmail.com> wrote in message
 news:mailman.901.1236111433.22690.digitalmars-d puremagic.com...
 On Tue, Mar 3, 2009 at 1:50 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:
 Tomasz Sowi&#324;ski wrote:
 Ideas for features based on the with.

 The with can make calling functions with enum arguments sexier. So
 instead
 of:
 auto d =3D dirEntries(".", SpanMode.breadth);

 you could say:
 auto d =3D dirEntries(".", breadth);

 by declaring the function as:
 dirEntries(string path, with SpanMode mode); // "with" does the trick

It looks nice, but has a subtle and disastrous problem. In D, argument=



 are
 fully resolved *before* overloading is done. If some of the overloads
 have
 with declarations, then there's a nightmarish problem of trying to mix
 overloading and argument resolution together.

What about the feature you mentioned at the D con, about being able to use enums without the enum name? =A0Or will/would that only be for things where it's really obvious, like switch statements?

Unless that was only for things like switch statements, I would hate that=

 I've used enums in languages that worked that way, and I found it to be s=

 a problematic namespace-clutterer that in those languages I always hack u=

 my enum definitions like this:

 enum Color
 {
 =A0 =A0Color_Red,
 =A0 =A0Color_Blue,
 =A0 =A0Color_Orange,
 =A0 =A0// etc...
 }

 Which is a style that I've always considered an ugly and kludgey, but
 unfortunately necessary, substitute for manditory enum names.

Oh, the way he described it in the slides was different. As in, normally you would use Color.Red, but inside a switch: switch(widgetColor) { case Red: // this is *completely* unambiguous } And such. Red is not a global; it's rather that name lookup is changed for some constructs.
Mar 03 2009