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digitalmars.D.learn - Can I count the of enum's fields at compile time?

reply Marc <jckj33 gmail.com> writes:
for example:

enum A { a = -10, b = -11, c = -12, d = -13, e = -34}

enum int countOfA = coutOfFields(A); // 5 fields
Nov 22 2017
next sibling parent reply Michael V. Franklin <slavo5150 yahoo.com> writes:
On Thursday, 23 November 2017 at 00:58:21 UTC, Marc wrote:

 for example:

 enum A { a = -10, b = -11, c = -12, d = -13, e = -34}

 enum int countOfA = coutOfFields(A); // 5 fields


https://dlang.org/spec/traits.html#allMembers

enum A { a = -10, b = -11, c = -12, d = -13, e = -34}

enum int countOfA = __traits(allMembers, A).length; // 5 fields

static assert(countOfA == 5);

Mike
Nov 22 2017
parent Marc <jckj33 gmail.com> writes:
On Thursday, 23 November 2017 at 01:01:42 UTC, Michael V. 
Franklin wrote:

 On Thursday, 23 November 2017 at 00:58:21 UTC, Marc wrote:

 for example:

 enum A { a = -10, b = -11, c = -12, d = -13, e = -34}

 enum int countOfA = coutOfFields(A); // 5 fields


 https://dlang.org/spec/traits.html#allMembers

 enum A { a = -10, b = -11, c = -12, d = -13, e = -34}

 enum int countOfA = __traits(allMembers, A).length; // 5 fields

 static assert(countOfA == 5);

 Mike


This was fast! Thanks
Nov 22 2017
prev sibling parent reply Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Thursday, November 23, 2017 00:58:21 Marc via Digitalmars-d-learn wrote:

 for example:

 enum A { a = -10, b = -11, c = -12, d = -13, e = -34}

 enum int countOfA = coutOfFields(A); // 5 fields


import std.traits;

enum countOfA = EnumMembers!A.length;

- Jonathna M Davis
Nov 22 2017
parent reply Marc <jckj33 gmail.com> writes:
On Thursday, 23 November 2017 at 01:04:29 UTC, Jonathan M Davis 
wrote:

 On Thursday, November 23, 2017 00:58:21 Marc via 
 Digitalmars-d-learn wrote:

 for example:

 enum A { a = -10, b = -11, c = -12, d = -13, e = -34}

 enum int countOfA = coutOfFields(A); // 5 fields


 import std.traits;

 enum countOfA = EnumMembers!A.length;

 - Jonathna M Davis


This sounds more readable. I was going to write a "function 
extension" to enum but I think it isn't really needed. Thank you 
too.
Nov 22 2017
parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 11/22/2017 05:21 PM, Marc wrote:

 On Thursday, 23 November 2017 at 01:04:29 UTC, Jonathan M Davis wrote:

 On Thursday, November 23, 2017 00:58:21 Marc via Digitalmars-d-learn 
 wrote:

 for example:

 enum A { a = -10, b = -11, c = -12, d = -13, e = -34}

 enum int countOfA = coutOfFields(A); // 5 fields


 import std.traits;

 enum countOfA = EnumMembers!A.length;

 - Jonathna M Davis


 
 This sounds more readable. I was going to write a "function extension" 
 to enum but I think it isn't really needed. Thank you too.


As an eponymous template:

enum One { a }
enum Three { a, b, c }

import std.range : EnumMembers;
enum countOf(E) = EnumMembers!E.length;

unittest {
     static assert(countOf!One == 1);
     static assert(countOf!Three == 3);
}

void main() {
}

Ali
Nov 22 2017
parent Marc <jckj33 gmail.com> writes:
On Thursday, 23 November 2017 at 01:34:54 UTC, Ali Çehreli wrote:

 On 11/22/2017 05:21 PM, Marc wrote:

 On Thursday, 23 November 2017 at 01:04:29 UTC, Jonathan M 
 Davis wrote:

 On Thursday, November 23, 2017 00:58:21 Marc via 
 Digitalmars-d-learn wrote:

 [...]


 import std.traits;

 enum countOfA = EnumMembers!A.length;

 - Jonathna M Davis


 
 This sounds more readable. I was going to write a "function 
 extension" to enum but I think it isn't really needed. Thank 
 you too.


 As an eponymous template:

 enum One { a }
 enum Three { a, b, c }

 import std.range : EnumMembers;
 enum countOf(E) = EnumMembers!E.length;

 unittest {
     static assert(countOf!One == 1);
     static assert(countOf!Three == 3);
 }

 void main() {
 }

 Ali


whoa, this is so easy and elegant. I'm falling in love with D. 
Thank you too!
Nov 22 2017