Re: mixin issue
On Wednesday, 29 November 2023 at 13:31:14 UTC, DLearner wrote: ``` Error: found `End of File` when expecting `;` following statement ``` If an extra ; is added: ``` }(` ~ strStartPtr ~ `,` ~ strPLPtr ~ `);`; ``` it works but doesn't seem correct. This is an annoying limitation of the D compiler. The root of the problem is that there is an ambiguity in D's grammar. When the compiler sees mixin(whatever); ...it cannot tell whether it's supposed to be a [Mixin Statement][1], or an [Expression Statement][2] that contains a [Mixin Expression][3]. If it's a Mixin Statement, then there should be a semicolon inside the mixin. If it's an Expression Statement with a Mixin Expression, then there shouldn't be a semicolon inside the mixin. To resolve this ambiguity, the compiler (currently) *assumes* that it's always a Mixin Statement, which means that it will always require a semicolon inside the mixin. As a result, it is impossible to write a string mixin that can be used as both a statement and an expression. If you have an expression mixin and you would like to use it as a statement, you can work around this limitation by adding `cast(void)` in front of the mixin: cast(void) mixin(whatever); This forces the compiler to parse the line as an Expression Statement containing a [Cast Expression][4], but does not otherwise change the meaning of the code. [1]: https://dlang.org/spec/statement.html#mixin-statement [2]: https://dlang.org/spec/statement.html#expression-statement [3]: https://dlang.org/spec/expression.html#mixin_expressions [4]: https://dlang.org/spec/expression.html#cast_expressions
Re: mixin issue
On Wednesday, 29 November 2023 at 13:31:14 UTC, DLearner wrote: it works but doesn't seem correct. You're mixing in an expression that creates an empty function and calls it. What do you want it to do?
mixin issue
The code:
```
void main() {
struct SB {
char SBChrFld1;
char SBChrFld2;
int SBIntFld1;
int SBIntFld2;
}
SB SBVar;
SB* wkSBPtr;
void* StartPtr1 = null;
mixin(mxnDelMbr("StartPtr1", "wkSBPtr"));
return;
}
string mxnDelMbr()(string strStartPtr, string strPLPtr) {
return `(void* StartPtr, typeof(` ~ strPLPtr ~ `) PLPtr) {
}(` ~ strStartPtr ~ `,` ~ strPLPtr ~ `)`;
}
```
Fails with:
```
Error: found `End of File` when expecting `;` following statement
```
If an extra ; is added:
```
}(` ~ strStartPtr ~ `,` ~ strPLPtr ~ `);`;
```
it works but doesn't seem correct.
Further, example above cloned from several other similar
examples, which
not only work, but if ';' introduced in corresponding place, dmd
complains with
empty statement deprecation.
FWIW only difference identified between successful examples and
this one,
is that other functions all return something, this one does not.
Suggestions?
Re: Strange Mixin issue
On 03/05/2014 03:10 PM, Frustrated wrote:
>> assert(s.Do(1, 2.5) == 3.5);
> And this is exactly what I don't what!
Sorry, I've completely misunderstood. :)
> Do, in my case, is a ctfe used
> only at compile time to make it easy to generate code. It's not needed
> at runtime and does not belong anywhere.
So, you want to mixin what D() generates. The following example mixes in
a static member function and two variables to S:
// Makes a make() function that returns a T
string makeMakeFunc(T)()
{
import std.string;
return format("static %s make() { %s result; return result; }",
T.stringof, T.stringof);
}
unittest
{
assert(makeMakeFunc!int() ==
"static int make() { int result; return result; }",
makeMakeFunc!int());
}
// Declares a make() function that returns T[0] and two variables of types
// T[1], T[2], etc.
string DoImpl(T...)()
{
import std.conv;
string result;
size_t i = 0;
foreach (Type; T[1 .. $]) {
result ~= Type.stringof ~ " var" ~ i.to!string ~ ";\n";
++i;
}
result ~= makeMakeFunc!(T[0])();
return result;
}
unittest
{
assert(DoImpl!(int, double, long) ==
"double var0;
long var1;
static int make() { int result; return result; }");
}
// Declares a make() function that returns typeof(this) and two variables of
// types T[0], T[1], etc.
template Do(T...)
{
mixin(DoImpl!(typeof(this), T)());
}
struct S
{
mixin Do!(int, double);
}
void main()
{
// S has a static member function that makes an S:
auto s = S.make();
static assert(is (typeof(s) == S));
// S has gained two member variables:
static assert(is (typeof(s.var0) == int));
static assert(is (typeof(s.var1) == double));
}
Ali
Re: Strange Mixin issue
On Wednesday, 5 March 2014 at 23:33:25 UTC, Frustrated wrote:
Maybe the problem isn't what I thought it was. I created a test
case that works:
import std.stdio, std.cstream;
mixin template C()
{
alias A = typeof(this);
mixin(B!(A));
}
template B(T)
{
pragma(msg, T);
enum B() { return "string foo() { return `<"~T.stringof~">`;
}"; }
}
class A
{
//mixin(B!(A));
mixin C;
}
void main()
{
auto a = new A;
writeln(a.foo());
//a.B();
din.getc();
}
Note the difference in calls. C is much easier because you
don't have to pass the parent type. This is all I'm trying to
achieve in the other code but when I do the functions(foo in
this case) do not get mixed in.
The actual error is quite strange in the other code:
When I simply wrap the code in an outside template I get the
error(s)
Eror: gui.border is not an lvalue
which is related to the line
auto ress = (gui.border = bb);
which works when I don't wrap the code. If I stick the output of
the string mixin template directly into the class, it works fine.
(so it has something to do wtih the template generation rather
than what it generates)
e.g., this is what I did
template AbstractToInterface(B, T...)
{
enum AbstractToInterface() { }
}
to
mixin template AbstractToInterface(B, T...)
{
mixin(AbstractToInterface2!(B, T));
}
template AbstractToInterface2(B, T...)
{
enum AbstractToInterface2() { }
}
and convert
mixin(AbstractToInterface!(WindowsGui, iButton, WindowsButton,
iBorder, WindowsBorder));
to
mixin AbstractToInterface!(WindowsGui, iButton, WindowsButton,
iBorder, WindowsBorder);
and I get the error down the road about
Eror: gui.border is not an lvalue
Which I guess is saying border does not have a setter, which is
what AbstractToInterface is suppose to be creating and adding...
again, it works when I copy the output of the template direct to
the class.
I'm betting it's a bug unless I'm doing something real stupid.
Re: Strange Mixin issue
Maybe the problem isn't what I thought it was. I created a test
case that works:
import std.stdio, std.cstream;
mixin template C()
{
alias A = typeof(this);
mixin(B!(A));
}
template B(T)
{
pragma(msg, T);
enum B() { return "string foo() { return `<"~T.stringof~">`; }";
}
}
class A
{
//mixin(B!(A));
mixin C;
}
void main()
{
auto a = new A;
writeln(a.foo());
//a.B();
din.getc();
}
Note the difference in calls. C is much easier because you don't
have to pass the parent type. This is all I'm trying to achieve
in the other code but when I do the functions(foo in this case)
do not get mixed in.
Re: Strange Mixin issue
On Wednesday, 5 March 2014 at 23:04:06 UTC, Ali Çehreli wrote:
On 03/05/2014 02:37 PM, Frustrated wrote:
>> import std.typetuple;
>>
>> template fooImpl(T...)
>> {
>> static assert(is (T[0] == S));// <-- COOL!
>> static assert(is (T[1] == int));
>> static assert(is (T[2] == double));
>> }
>>
>> template foo(T...)
>> {
>> alias foo = fooImpl!(TypeTuple!(typeof(this), T));
>> }
>>
>> struct S
>> {
>> mixin foo!(int, double);
>> }
>>
>> void main()
>> {
>> auto s = S();
>> }
>>
>> Ali
>
> this is not quite the same.
I think you tried to give a link in your original code but it
is missing. Still, it is very difficult for me to follow code
unless it is really simple. :)
> You have static asserts.
Just to prove that I've managed to inject typeof(this) as the
first template parameter.
> I'm trying to avoid
> mixing in ctfe code that might interfer with the class. (I
have a temp
> function Do which if I mixin as a normal template will mixin
Do into the
> class make Do a member of that class)
The following is what I understand so far. :) The last line of
main() proves that S gained a function Do() that takes (int,
double) parameters.
import std.typetuple;
template DoImpl(T...)
{
auto Do(T[1] p1, T[2] p2)
{
return p1 + p2;
}
}
template Do(T...)
{
mixin DoImpl!(TypeTuple!(typeof(this), T));
}
struct S
{
mixin Do!(int, double);
}
void main()
{
auto s = S();
assert(s.Do(1, 2.5) == 3.5);
}
Ali
And this is exactly what I don't what! Do, in my case, is a ctfe
used only at compile time to make it easy to generate code. It's
not needed at runtime and does not belong anywhere.
Re: Strange Mixin issue
On 03/05/2014 03:04 PM, Ali Çehreli wrote:
template Do(T...)
{
mixin DoImpl!(TypeTuple!(typeof(this), T));
Actually, TypeTuple is not needed there:
mixin DoImpl!(typeof(this), T);
Ali
Re: Strange Mixin issue
On 03/05/2014 02:37 PM, Frustrated wrote:
>> import std.typetuple;
>>
>> template fooImpl(T...)
>> {
>> static assert(is (T[0] == S));// <-- COOL!
>> static assert(is (T[1] == int));
>> static assert(is (T[2] == double));
>> }
>>
>> template foo(T...)
>> {
>> alias foo = fooImpl!(TypeTuple!(typeof(this), T));
>> }
>>
>> struct S
>> {
>> mixin foo!(int, double);
>> }
>>
>> void main()
>> {
>> auto s = S();
>> }
>>
>> Ali
>
> this is not quite the same.
I think you tried to give a link in your original code but it is
missing. Still, it is very difficult for me to follow code unless it is
really simple. :)
> You have static asserts.
Just to prove that I've managed to inject typeof(this) as the first
template parameter.
> I'm trying to avoid
> mixing in ctfe code that might interfer with the class. (I have a temp
> function Do which if I mixin as a normal template will mixin Do into the
> class make Do a member of that class)
The following is what I understand so far. :) The last line of main()
proves that S gained a function Do() that takes (int, double) parameters.
import std.typetuple;
template DoImpl(T...)
{
auto Do(T[1] p1, T[2] p2)
{
return p1 + p2;
}
}
template Do(T...)
{
mixin DoImpl!(TypeTuple!(typeof(this), T));
}
struct S
{
mixin Do!(int, double);
}
void main()
{
auto s = S();
assert(s.Do(1, 2.5) == 3.5);
}
Ali
Re: Strange Mixin issue
On 03/05/2014 01:30 PM, Frustrated wrote:
I am trying to remove the unnecessary passing of the type of class to a
template but can't seem to get it to work:
see
The code is the
mixin(AbstractToInterface!(WindowsGui, iButton, WindowsButton,
iBorder, WindowsBorder));
which I want to not have to specify WindowsGui.
I've tried wrapping AbstractToInterface in a mixin template and use that
and typeof(this) but then the mixin of the mixin does not get mixed in
to the class
e.g.,
mixin template AbstractToInterface2(T...)
{
mixin(AbstractToInterface!(typeof(this), T));
}
Then use mixin AbstractTointerface2!(iButton, WindowsButton, iBorder,
WindowsBorder).
It's probably something stupid but I can't seem to get it to work(have a
very similar case in some other code and it works fine... the only
difference is I'm not using nested mixins.
The following works for me maybe because the templates are not mixin
templates. What's a mixin template again?
import std.typetuple;
template fooImpl(This, T...)
{
static assert(is (This == S));// <-- IT WORKED!
static assert(is (T == TypeTuple!(int, double)));
}
template foo(T...)
{
alias foo = fooImpl!(typeof(this), T);
}
struct S
{
mixin foo!(int, double);
}
void main()
{
auto s = S();
}
Even better:
import std.typetuple;
template fooImpl(T...)
{
static assert(is (T[0] == S));// <-- COOL!
static assert(is (T[1] == int));
static assert(is (T[2] == double));
}
template foo(T...)
{
alias foo = fooImpl!(TypeTuple!(typeof(this), T));
}
struct S
{
mixin foo!(int, double);
}
void main()
{
auto s = S();
}
Ali
Re: Strange Mixin issue
On Wednesday, 5 March 2014 at 22:35:46 UTC, Ali Çehreli wrote:
On 03/05/2014 01:30 PM, Frustrated wrote:
I am trying to remove the unnecessary passing of the type of
class to a
template but can't seem to get it to work:
see
The code is the
mixin(AbstractToInterface!(WindowsGui, iButton,
WindowsButton,
iBorder, WindowsBorder));
which I want to not have to specify WindowsGui.
I've tried wrapping AbstractToInterface in a mixin template
and use that
and typeof(this) but then the mixin of the mixin does not get
mixed in
to the class
e.g.,
mixin template AbstractToInterface2(T...)
{
mixin(AbstractToInterface!(typeof(this), T));
}
Then use mixin AbstractTointerface2!(iButton, WindowsButton,
iBorder,
WindowsBorder).
It's probably something stupid but I can't seem to get it to
work(have a
very similar case in some other code and it works fine... the
only
difference is I'm not using nested mixins.
The following works for me maybe because the templates are not
mixin templates. What's a mixin template again?
import std.typetuple;
template fooImpl(This, T...)
{
static assert(is (This == S));// <-- IT WORKED!
static assert(is (T == TypeTuple!(int, double)));
}
template foo(T...)
{
alias foo = fooImpl!(typeof(this), T);
}
struct S
{
mixin foo!(int, double);
}
void main()
{
auto s = S();
}
Even better:
import std.typetuple;
template fooImpl(T...)
{
static assert(is (T[0] == S));// <-- COOL!
static assert(is (T[1] == int));
static assert(is (T[2] == double));
}
template foo(T...)
{
alias foo = fooImpl!(TypeTuple!(typeof(this), T));
}
struct S
{
mixin foo!(int, double);
}
void main()
{
auto s = S();
}
Ali
this is not quite the same. You have static asserts. I'm trying
to avoid mixing in ctfe code that might interfer with the class.
(I have a temp function Do which if I mixin as a normal template
will mixin Do into the class make Do a member of that class)
Strange Mixin issue
I am trying to remove the unnecessary passing of the type of
class to a template but can't seem to get it to work:
see
The code is the
mixin(AbstractToInterface!(WindowsGui, iButton, WindowsButton,
iBorder, WindowsBorder));
which I want to not have to specify WindowsGui.
I've tried wrapping AbstractToInterface in a mixin template and
use that and typeof(this) but then the mixin of the mixin does
not get mixed in to the class
e.g.,
mixin template AbstractToInterface2(T...)
{
mixin(AbstractToInterface!(typeof(this), T));
}
Then use mixin AbstractTointerface2!(iButton, WindowsButton,
iBorder, WindowsBorder).
It's probably something stupid but I can't seem to get it to
work(have a very similar case in some other code and it works
fine... the only difference is I'm not using nested mixins.
Re: Template Mixin issue
Christopher Wright wrote: Mike L. wrote: If the compiler can tell that B!(int) is a type, why can't it tell that it is a child class of A!(int) ? This is a bug. In template specializations, : means equality. In static if, : means convertibility. This is only with template specializations involving templates, by the way. Template specializations involving any other type are fine.
Re: Template Mixin issue
Mike L. wrote:
If the compiler can tell that B!(int) is a type, why can't it tell that it is a
child class of A!(int) ?
This is a bug. In template specializations, : means equality. In static
if, : means convertibility.
So, you can use:
template ADefaults(Type, AType)
{
static assert (is (AType : A!(Type)));
Type blah()
{ return Type.init; }
}
http://d.puremagic.com/issues/show_bug.cgi?id=1715 if you want to vote.
Template Mixin issue
Hello,
I was wondering why the following does not work:
interface A(Type)
{ Type blah(); }
template ADefaults(Type, AType : A!(Type))
{
Type blah()
{ return Type.init; }
}
class B(Type) : A!(Type)
{ mixin ADefaults!(Type, B!(Type)); }
void main()
{ auto x = new B!(int)(); }
It gives the error: test.d(11): mixin ADefault!(int,B) does not match any
template declaration
However, it will compile if you change the ADefaults header to:
template ADefaults(Type, AType)
If the compiler can tell that B!(int) is a type, why can't it tell that it is a
child class of A!(int) ?
