Re: Trying to get type and name at compile time
On Tuesday, 24 May 2016 at 18:44:45 UTC, ag0aep6g wrote: Seems to be a problem in ApplyLeft: import std.meta: AliasSeq, ApplyLeft; alias addType(T, string name) = AliasSeq!(T, name); alias addTypeInt = ApplyLeft!(addType, int); alias FullyInstantiated = addTypeInt!"foo"; Fails with: "std/meta.d(1114): Error: cannot interpret int at compile time". I've filed an issue: https://issues.dlang.org/show_bug.cgi?id=16070 Thanks! I've worked around it for now with some recursion :) Using `is(...)` with an AliasSeq of only types is ok. But you can't use it when there's a non-type in the sequence. That makes sense. Thanks for the help, Edwin
Re: Trying to get type and name at compile time
On 05/24/2016 06:22 PM, Edwin van Leeuwen wrote: That's what I assumed at first.. So why does the following fail with: cannot interpret double at compile time? I assumed staticMap would automatically flatten the resulting AliasSeqs. ``` import std.meta : AliasSeq, ApplyLeft, staticMap; struct Point { double x; double y; } template addType(T,alias name) { alias addType = AliasSeq!( typeof(__traits(getMember, Point, name)), name ); } alias test3 = addType!( Point, "x" ); // I expected AliasSeq!(double,"x")??? pragma(msg,test3); // tuple((double), "x") //static assert(is(test == AliasSeq!(double,"x"))); alias ts = AliasSeq!("x","y"); alias addTypeP = ApplyLeft!(addType,Point); alias mapped = staticMap!(addTypeP,ts); pragma(msg,mapped); void main() { } ``` Seems to be a problem in ApplyLeft: import std.meta: AliasSeq, ApplyLeft; alias addType(T, string name) = AliasSeq!(T, name); alias addTypeInt = ApplyLeft!(addType, int); alias FullyInstantiated = addTypeInt!"foo"; Fails with: "std/meta.d(1114): Error: cannot interpret int at compile time". I've filed an issue: https://issues.dlang.org/show_bug.cgi?id=16070 [...] I thought so, but a lot of the documentation does seem to compare it (see the example here): https://dlang.org/library/std/meta/static_map.html Using `is(...)` with an AliasSeq of only types is ok. But you can't use it when there's a non-type in the sequence.
Re: Trying to get type and name at compile time
On Tuesday, 24 May 2016 at 15:09:43 UTC, Adam D. Ruppe wrote: On Tuesday, 24 May 2016 at 15:01:33 UTC, Edwin van Leeuwen wrote: // I expected AliasSeq!(double,"x")??? pragma(msg,test); // tuple((double), "x") What Phobos calls AliasSeq is called tuple inside the compiler. They are the same thing, just different names. That's what I assumed at first.. So why does the following fail with: cannot interpret double at compile time? I assumed staticMap would automatically flatten the resulting AliasSeqs. ``` import std.meta : AliasSeq, ApplyLeft, staticMap; struct Point { double x; double y; } template addType(T,alias name) { alias addType = AliasSeq!( typeof(__traits(getMember, Point, name)), name ); } alias test3 = addType!( Point, "x" ); // I expected AliasSeq!(double,"x")??? pragma(msg,test3); // tuple((double), "x") //static assert(is(test == AliasSeq!(double,"x"))); alias ts = AliasSeq!("x","y"); alias addTypeP = ApplyLeft!(addType,Point); alias mapped = staticMap!(addTypeP,ts); pragma(msg,mapped); void main() { } ``` Looking at it now, I guess it is because staticMap does not work with alias values, only with actual type lists. Is that correct? Any ideas on how to do this? static assert(is(test == AliasSeq!(double,"x"))); AliasSeq is not comparable as a type. You can test the individual pieces of it (`is(test[0] == double) && test[1] == "x"`) or wrap it in a struct or something. I thought so, but a lot of the documentation does seem to compare it (see the example here): https://dlang.org/library/std/meta/static_map.html
Re: Trying to get type and name at compile time
On Tuesday, 24 May 2016 at 15:01:33 UTC, Edwin van Leeuwen wrote: // I expected AliasSeq!(double,"x")??? pragma(msg,test); // tuple((double), "x") What Phobos calls AliasSeq is called tuple inside the compiler. They are the same thing, just different names. static assert(is(test == AliasSeq!(double,"x"))); AliasSeq is not comparable as a type. You can test the individual pieces of it (`is(test[0] == double) && test[1] == "x"`) or wrap it in a struct or something.
Trying to get type and name at compile time
Hi all, I am trying to get the type and name of a field at compile time, but can't get the following to work. Anyone any idea of why test is not of the type AliasSeq!(double, "x")? ``` import std.meta : AliasSeq; struct Point { double x; double y; } alias test = AliasSeq!( typeof(__traits(getMember, Point, "x")), "x" ); // I expected AliasSeq!(double,"x")??? pragma(msg,test); // tuple((double), "x") static assert(is(test == AliasSeq!(double,"x"))); void main() {} ``` Cheers, Edwin