• Chris Williams (21/21) Nov 25 2013 Is there any way to do something like this?
• IgorStepanov (13/34) Nov 25 2013 You can write
• Chris Williams (4/16) Nov 25 2013 Thank you. It looks like 2.063 only handled the first case (and
• Shammah Chancellor (3/29) Nov 25 2013 What is the practical purpose of such a thing?
• Chris Williams (13/15) Nov 25 2013 The two cases I can think of are:

"Chris Williams" <yoreanon-chrisw yahoo.co.jp> writes:

Is there any way to do something like this?

import std.stdio;

enum Foo : void function() {
	WOMBAT = () {writeln("Wombat");}
}

void doStuff(Foo f) {
	f();
}

int main() {
	doStuff( Foo.WOMBAT );
	
	return 0;
}

Currently, I get the errors:

hello.d(4): Error: non-constant nested delegate literal 
expression __lambda1
hello.d(12): Error: delegate hello.Foo.__lambda1 is a nested 
function and cannot be accessed from D main

I can fix it by declaring a function outside of Foo and setting 
WOMBAT = &fname, but it seems like I should be able to create a 
hidden lambda.

"IgorStepanov" <wazar mail.ru> writes:

On Monday, 25 November 2013 at 23:32:27 UTC, Chris Williams wrote:
 Is there any way to do something like this?

 import std.stdio;

 enum Foo : void function() {
 	WOMBAT = () {writeln("Wombat");}
 }

 void doStuff(Foo f) {
 	f();
 }

 int main() {
 	doStuff( Foo.WOMBAT );
 	
 	return 0;
 }

 Currently, I get the errors:

 hello.d(4): Error: non-constant nested delegate literal 
 expression __lambda1
 hello.d(12): Error: delegate hello.Foo.__lambda1 is a nested 
 function and cannot be accessed from D main

 I can fix it by declaring a function outside of Foo and setting 
 WOMBAT = &fname, but it seems like I should be able to create a 
 hidden lambda.

You can write

enum Foo : void function()
{
     WOMBAT = function void () {writeln("Wombat");}
}

or

enum Foo
{
     WOMBAT = function void () {writeln("Wombat");}
}

`() {writeln("Wombat");}` literal recognized by compiler as 
delegate, not function.

"Chris Williams" <yoreanon-chrisw yahoo.co.jp> writes:

On Tuesday, 26 November 2013 at 00:27:25 UTC, IgorStepanov wrote:
 You can write

 enum Foo : void function()
 {
     WOMBAT = function void () {writeln("Wombat");}
 }

 or

 enum Foo
 {
     WOMBAT = function void () {writeln("Wombat");}
 }

 `() {writeln("Wombat");}` literal recognized by compiler as 
 delegate, not function.

Thank you. It looks like 2.063 only handled the first case (and 
only if there was a single entry), but with 2.064 it works 
perfectly.

Shammah Chancellor <anonymous coward.com> writes:

On 2013-11-25 23:32:25 +0000, Chris Williams said:

 Is there any way to do something like this?
 
 import std.stdio;
 
 enum Foo : void function() {
 	WOMBAT = () {writeln("Wombat");}
 }
 
 void doStuff(Foo f) {
 	f();
 }
 
 int main() {
 	doStuff( Foo.WOMBAT );
 	
 	return 0;
 }
 
 Currently, I get the errors:
 
 hello.d(4): Error: non-constant nested delegate literal expression __lambda1
 hello.d(12): Error: delegate hello.Foo.__lambda1 is a nested function 
 and cannot be accessed from D main
 
 I can fix it by declaring a function outside of Foo and setting WOMBAT 
 = &fname, but it seems like I should be able to create a hidden lambda.

What is the practical purpose of such a thing?

-Shammah

"Chris Williams" <yoreanon-chrisw yahoo.co.jp> writes:

On Tuesday, 26 November 2013 at 05:13:00 UTC, Shammah Chancellor 
wrote:
 What is the practical purpose of such a thing?

 -Shammah

The two cases I can think of are:

1. To define a set of supported handlers which can be passed in 
as a parameter to a call. Rather than writing a switch in your 
method that calls the correct function, based on the supported 
values in the enum, you build the handlers right into the enum. 
It pulls your code into one.

2. If you have a quick and easy method for serializing an enum - 
for example, converting the name to a string and back - then you 
can write can write code that deserializes and calls a function 
in a single line.

But mostly, I was just curious.