digitalmars.D.learn - Setting a list of values

Joel (7/7) Apr 30 2016 This has no effect:

=?UTF-8?Q?Ali_=c3=87ehreli?= (19/21) Apr 30 2016 This is a common issue especially for people who know lambdas from other...

Marc =?UTF-8?B?U2Now7x0eg==?= (3/25) May 01 2016 Or, remove the arrow:
Xinok (8/16) May 01 2016 Those are some discrete semantics. I know D pretty well and even

=?UTF-8?Q?Ali_=c3=87ehreli?= (9/23) May 02 2016 A warning would be great but I don't see how it can cover all cases. A

Marc =?UTF-8?B?U2Now7x0eg==?= (12/42) May 02 2016 Warning (better: disallowing altogether) about `=>` directly

sigod (2/15) May 02 2016 It's good idea. I myself stumbled into this before.

Steven Schveighoffer (3/22) May 02 2016 Agree.

sigod (2/31) May 07 2016 https://issues.dlang.org/show_bug.cgi?id=16001

Brian Schott (3/4) May 07 2016 In other words it's trivial for D-Scanner to warn about this.

Joel (3/26) May 03 2016 This seems to work the best:

sigod (2/6) May 07 2016 And the ugliest. And probably slowest.

Joel <joelcnz gmail.com> writes:

This has no effect:
_bars.each!(a => { a._plots.fillColor = Color(255, 180, 0); });

I tried putting ..each!((ref a) =>.. with no difference

This works:
foreach(b; _bars) {
	b._plots.fillColor = Color(255, 180, 0);
}

Apr 30 2016

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 04/30/2016 10:05 PM, Joel wrote:
 This has no effect:
 _bars.each!(a => { a._plots.fillColor = Color(255, 180, 0); });

This is a common issue especially for people who know lambdas from other 
languages. :)

Your lambda does not do any work. Rather, your lambda returns another 
lambda, which is promptly ignored:

import std.stdio;
import std.algorithm;

void main() {
     auto arr = [ 1, 2 ];
     arr.each!(a => { writeln(a); });  // returns lambda for each a
}

The lambda that 'each' takes above is "given a, produce this lambda". . 
To do the intended work, you need to remove the curly braces (and the 
semicolon):

     arr.each!(a => writeln(a));

Or, you could insert empty () to call the returned lambda but that would 
completely be extra work in this case:

     arr.each!(a => { writeln(a); }());

Ali

Apr 30 2016

Marc =?UTF-8?B?U2Now7x0eg==?= <schuetzm gmx.net> writes:

On Sunday, 1 May 2016 at 05:42:00 UTC, Ali Çehreli wrote:
 On 04/30/2016 10:05 PM, Joel wrote:
 This has no effect:
 _bars.each!(a => { a._plots.fillColor = Color(255, 180, 0);

 });

 This is a common issue especially for people who know lambdas 
 from other languages. :)

 Your lambda does not do any work. Rather, your lambda returns 
 another lambda, which is promptly ignored:

 import std.stdio;
 import std.algorithm;

 void main() {
     auto arr = [ 1, 2 ];
     arr.each!(a => { writeln(a); });  // returns lambda for 
 each a
 }

 The lambda that 'each' takes above is "given a, produce this 
 lambda". . To do the intended work, you need to remove the 
 curly braces (and the semicolon):

     arr.each!(a => writeln(a));

 Or, you could insert empty () to call the returned lambda but 
 that would completely be extra work in this case:

     arr.each!(a => { writeln(a); }());

Or, remove the arrow:

     arr.each!((a) { writeln(a); });

May 01 2016

Xinok <xinok live.com> writes:

On Sunday, 1 May 2016 at 05:42:00 UTC, Ali Çehreli wrote:
 On 04/30/2016 10:05 PM, Joel wrote:
 This has no effect:
 _bars.each!(a => { a._plots.fillColor = Color(255, 180, 0);

 });

 This is a common issue especially for people who know lambdas 
 from other languages. :)

 Your lambda does not do any work. Rather, your lambda returns 
 another lambda, which is promptly ignored:

Those are some discrete semantics. I know D pretty well and even 
I didn't see the problem initially. Anybody else think it's worth 
adding a warning to the compiler for this specific case? If this 
is the user's intended behavior, then they can rewrite it like 
this to be explicit and disable the warning:

_bars.each!(a => (){ a._plots.fillColor = Color(255, 180, 0); });
//               ^^ add empty parenthesis before the curly brace

May 01 2016

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 05/01/2016 12:54 PM, Xinok wrote:
 On Sunday, 1 May 2016 at 05:42:00 UTC, Ali Çehreli wrote:
 On 04/30/2016 10:05 PM, Joel wrote:
 This has no effect:
 _bars.each!(a => { a._plots.fillColor = Color(255, 180, 0);

 });

 This is a common issue especially for people who know lambdas from
 other languages. :)

 Your lambda does not do any work. Rather, your lambda returns another
 lambda, which is promptly ignored:

 Those are some discrete semantics. I know D pretty well and even I
 didn't see the problem initially. Anybody else think it's worth adding a
 warning to the compiler for this specific case?

A warning would be great but I don't see how it can cover all cases. A 
special warning for std.algorithm.each might work but this exact issue 
appeared on the main thread just a few minutes ago:

   http://forum.dlang.org/post/qsayoktyffczskrnmgxu forum.dlang.org

     alias funType = void function(int x);
     funType fun = (x) => { assert(x); };   // cannot return non-void 
from void function

Ali

May 02 2016

Marc =?UTF-8?B?U2Now7x0eg==?= <schuetzm gmx.net> writes:

On Monday, 2 May 2016 at 08:46:31 UTC, Ali Çehreli wrote:
 On 05/01/2016 12:54 PM, Xinok wrote:
 On Sunday, 1 May 2016 at 05:42:00 UTC, Ali Çehreli wrote:
 On 04/30/2016 10:05 PM, Joel wrote:
 This has no effect:
 _bars.each!(a => { a._plots.fillColor = Color(255, 180, 0);

 });

 This is a common issue especially for people who know


 lambdas from
 other languages. :)

 Your lambda does not do any work. Rather, your lambda


 returns another
 lambda, which is promptly ignored:

 Those are some discrete semantics. I know D pretty well and

 even I
 didn't see the problem initially. Anybody else think it's

 worth adding a
 warning to the compiler for this specific case?

 A warning would be great but I don't see how it can cover all 
 cases. A special warning for std.algorithm.each might work but 
 this exact issue appeared on the main thread just a few minutes 
 ago:

   
 http://forum.dlang.org/post/qsayoktyffczskrnmgxu forum.dlang.org

     alias funType = void function(int x);
     funType fun = (x) => { assert(x); };   // cannot return 
 non-void from void function

 Ali

Warning (better: disallowing altogether) about `=>` directly 
followed by `{` should be enough to cover all cases. To express 
that you really want a lambda returning a lambda, it can be 
rewritten either as:

     (x) => () { assert(x); }

or as:

     (x) => ({ assert(x); })

This check can be done purely by looking at the tokens. Should we 
someday introduce tuples with `{}`, the check needs to be done 
after the node starting with `{` has been parsed to distinguish 
between delegate and tuple literals.

May 02 2016

sigod <sigod.mail gmail.com> writes:

On Monday, 2 May 2016 at 10:15:04 UTC, Marc Schütz wrote:
 On Monday, 2 May 2016 at 08:46:31 UTC, Ali Çehreli wrote:
 [...]

 Warning (better: disallowing altogether) about `=>` directly 
 followed by `{` should be enough to cover all cases. To express 
 that you really want a lambda returning a lambda, it can be 
 rewritten either as:

     (x) => () { assert(x); }

 or as:

     (x) => ({ assert(x); })

 This check can be done purely by looking at the tokens. Should 
 we someday introduce tuples with `{}`, the check needs to be 
 done after the node starting with `{` has been parsed to 
 distinguish between delegate and tuple literals.

It's good idea. I myself stumbled into this before.

May 02 2016

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 5/2/16 6:00 PM, sigod wrote:
 On Monday, 2 May 2016 at 10:15:04 UTC, Marc Schütz wrote:
 On Monday, 2 May 2016 at 08:46:31 UTC, Ali Çehreli wrote:
 [...]

 Warning (better: disallowing altogether) about `=>` directly followed
 by `{` should be enough to cover all cases. To express that you really
 want a lambda returning a lambda, it can be rewritten either as:

     (x) => () { assert(x); }

 or as:

     (x) => ({ assert(x); })

 This check can be done purely by looking at the tokens. Should we
 someday introduce tuples with `{}`, the check needs to be done after
 the node starting with `{` has been parsed to distinguish between
 delegate and tuple literals.

 It's good idea. I myself stumbled into this before.

Agree.

-Steve

May 02 2016

sigod <sigod.mail gmail.com> writes:

On Monday, 2 May 2016 at 23:41:39 UTC, Steven Schveighoffer wrote:
 On 5/2/16 6:00 PM, sigod wrote:
 On Monday, 2 May 2016 at 10:15:04 UTC, Marc Schütz wrote:
 On Monday, 2 May 2016 at 08:46:31 UTC, Ali Çehreli wrote:
 [...]

 Warning (better: disallowing altogether) about `=>` directly 
 followed
 by `{` should be enough to cover all cases. To express that 
 you really
 want a lambda returning a lambda, it can be rewritten either 
 as:

     (x) => () { assert(x); }

 or as:

     (x) => ({ assert(x); })

 This check can be done purely by looking at the tokens. 
 Should we
 someday introduce tuples with `{}`, the check needs to be 
 done after
 the node starting with `{` has been parsed to distinguish 
 between
 delegate and tuple literals.

 It's good idea. I myself stumbled into this before.

 Agree.

 -Steve

https://issues.dlang.org/show_bug.cgi?id=16001

May 07 2016

Brian Schott <briancschott gmail.com> writes:

On Monday, 2 May 2016 at 10:15:04 UTC, Marc Schütz wrote:
 This check can be done purely by looking at the tokens.

In other words it's trivial for D-Scanner to warn about this.

https://github.com/Hackerpilot/Dscanner/issues/341

May 07 2016

Joel <joelcnz gmail.com> writes:

On Sunday, 1 May 2016 at 05:42:00 UTC, Ali Çehreli wrote:
 On 04/30/2016 10:05 PM, Joel wrote:
 This has no effect:
 _bars.each!(a => { a._plots.fillColor = Color(255, 180, 0);

 });

 This is a common issue especially for people who know lambdas 
 from other languages. :)

 Your lambda does not do any work. Rather, your lambda returns 
 another lambda, which is promptly ignored:

 import std.stdio;
 import std.algorithm;

 void main() {
     auto arr = [ 1, 2 ];
     arr.each!(a => { writeln(a); });  // returns lambda for 
 each a
 }

 The lambda that 'each' takes above is "given a, produce this 
 lambda". . To do the intended work, you need to remove the 
 curly braces (and the semicolon):

     arr.each!(a => writeln(a));

 Or, you could insert empty () to call the returned lambda but 
 that would completely be extra work in this case:

     arr.each!(a => { writeln(a); }());

 Ali

This seems to work the best:

arr.each!(a => { writeln(a); }());

May 03 2016

sigod <sigod.mail gmail.com> writes:

On Wednesday, 4 May 2016 at 04:56:54 UTC, Joel wrote:
 On Sunday, 1 May 2016 at 05:42:00 UTC, Ali Çehreli wrote:
 [...]

 This seems to work the best:

 arr.each!(a => { writeln(a); }());

And the ugliest. And probably slowest.

May 07 2016

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digitalmars.D.learn - Setting a list of values