• aliak (38/38) Jan 22 2018 Hi, I'm trying to get a list of only member functions of a
• aliak (8/10) Jan 22 2018 And a follow up question: should I be using static foreach in
• thedeemon (12/16) Jan 23 2018 The struct defined inside a scope can mention variables defined
• aliak (2/15) Jan 24 2018 Ah makes sense. Thanks!

aliak <something something.com> writes:

Hi, I'm trying to get a list of only member functions of a 
struct. I've found that if you do not declare a struct as static 
inside a scope, then there's a hidden "this" member as part of 
the struct. Can someone explain the logic there?

Also am I going about this correctly?

template MemberFunctions(T) {
     import std.traits: isFunction;
     auto MemberFunctions() {
         string[] memberFunctions;
         foreach (member; __traits(allMembers, T)) {

             // NOTE: This static if is here is because of that 
hidden "this" member
             //
             // if I do not do this then I get:
             //   Error: identifier expected following ., not this

             static if (is(typeof(mixin("T." ~ member)) F))
             	if (isFunction!F) {
                     memberFunctions ~= member;
	        }
         }
         return memberFunctions;
     }
}

unittest {
     // works for static and non static.
     /* static */ struct A {
         void opCall() {}
         void g() {}
     }

     /* static */ struct B {
         int m;
         A a;
         alias a this;
         void f() {}
     }

     static assert(MemberFunctions!B == ["f"]);
}

Cheers

aliak <something something.com> writes:

On Tuesday, 23 January 2018 at 00:00:38 UTC, aliak wrote:
 Hi, I'm trying to get a list of only member functions of a [...]
 Cheers

And a follow up question: should I be using static foreach in 
there instead of a normal foreach? i.e.

foreach (member; __traits(allMembers, T)) {{
     // same code
}}

And why if yes

Thanks again!

thedeemon <dlang thedeemon.com> writes:

On Tuesday, 23 January 2018 at 00:00:38 UTC, aliak wrote:
 Hi, I'm trying to get a list of only member functions of a 
 struct. I've found that if you do not declare a struct as 
 static inside a scope, then there's a hidden "this" member as 
 part of the struct. Can someone explain the logic there?

The struct defined inside a scope can mention variables defined 
in that scope (e.g. use them in its methods), so it needs a 
pointer to the place where those closed variables live. That's 
the main difference between such struct and a static one that 
cannot use those scope vars. I guess you're seeing that pointer 
as additional member.


As for static foreach, when you write a simple foreach over some 
compile-time tuple (like in this case), it's unrolled at compile 
time similarly to "static foreach", the main difference is 
whether it creates a sub-scope for the loop body or not. 
"foreach" creates one, "static foreach" doesn't.

aliak <something something.com> writes:

On Wednesday, 24 January 2018 at 07:55:01 UTC, thedeemon wrote:
 On Tuesday, 23 January 2018 at 00:00:38 UTC, aliak wrote:
 [...]

 The struct defined inside a scope can mention variables defined 
 in that scope (e.g. use them in its methods), so it needs a 
 pointer to the place where those closed variables live. That's 
 the main difference between such struct and a static one that 
 cannot use those scope vars. I guess you're seeing that pointer 
 as additional member.


 As for static foreach, when you write a simple foreach over 
 some compile-time tuple (like in this case), it's unrolled at 
 compile time similarly to "static foreach", the main difference 
 is whether it creates a sub-scope for the loop body or not. 
 "foreach" creates one, "static foreach" doesn't.

Ah makes sense. Thanks!