Why is this pure?
The following program compiles, and does what you'd expect:
struct A {
int a;
}
pure int func( ref A a )
{
return a.a += 3;
}
As far as I can tell, however, it shouldn't. I don't see how or
why func can possibly be considered pure, as it changes a state
external to the function.
What am I missing? Or is this just a compiler bug?
Shachar
Re: Why is this pure?
On Monday, 25 August 2014 at 06:27:00 UTC, Shachar wrote:
The following program compiles, and does what you'd expect:
struct A {
int a;
}
pure int func( ref A a )
{
return a.a += 3;
}
As far as I can tell, however, it shouldn't. I don't see how or
why func can possibly be considered pure, as it changes a state
external to the function.
What am I missing? Or is this just a compiler bug?
Shachar
http://klickverbot.at/blog/2012/05/purity-in-d/
Re: Why no multiple-dispatch?
On Monday, 25 August 2014 at 02:04:43 UTC, Aerolite wrote: On Monday, 25 August 2014 at 01:34:14 UTC, Idan Arye wrote: On Monday, 25 August 2014 at 01:10:32 UTC, Aerolite wrote: -- No syntax modification (unless you want the feature to be optional) If this ever gets into the core language, it absolutely must be optional! Think of the implications of having this as the default and only behavior: * Every overloaded function will have to do a runtime typecheck - this not only causes a usually unnecessary overhead but also has a negative impact on branch prediction. Well, you'd only have to resolve *class* parameters (since obviously literals and structs don't support inheritance). My brain is a little foggy at the moment due to this nice flu I have, but do we even need to do this at run-time? It's not like we can do a Java and use run-time reflection to create new class instances. The closest thing we have to that is Object.factory, but that's all compile-time built and type-safe as far as I'm aware? Or am I being silly? If multi-dispatching is done at compile-time, it can't rely on the object's runtime type - only on the static type of the reference that holds it. This is no different than regular function overloading that we already have. * What if you have multiple overloads that happen to be templated? Now the compiler will have to instantiate them all! Hard to say, although surely there could be some examination of what is and is not necessary to instantiate. This is again making the implementation a tad more complicated, though. That said, if something like @multimethod existed, it would assist in this matter. Are you suggesting the compiler will try to resolve the polymorphism at compile-time, looking at all possible paths that lead to a function call to check all possible runtime values it's object arguments can get? Anyways, I don't think you get just how strong this language's tendency to push features to the library is, so I'd like to point you to this post by the language's creator: http://forum.dlang.org/thread/lt00a9$2uoe$1...@digitalmars.com#post-lt00a9:242uoe:241:40digitalmars.com Heh. Well, that's Walter for you! :P But I definitely understand the push towards the library. I just feel that handling method dispatch, even in compile-time template code, is not something that we should really be writing ourselves. It's like trying to do virtual method calls in C! Virtual methods in C can be done with GObject - though the syntax is awkward. D is so much better than C when it comes to metaprogramming, that the syntax for multimethods wouldn't be awkward(unless you consider anything that's not burned to the core syntax awkward)
Re: Why no multiple-dispatch?
On Monday, 25 August 2014 at 07:36:22 UTC, Idan Arye wrote: Are you suggesting the compiler will try to resolve the polymorphism at compile-time, looking at all possible paths that lead to a function call to check all possible runtime values it's object arguments can get? I've argued for whole program analysis before and this is another example where it would be useful :-). When you have figured out the worst-case use pattern you can either make one function virtual and then inline the others as a switch or you can create class-ids that can be hashed perfectly to an array of function pointers. However, why do you want multiple dispatch? I cannot think of any application level use scenario where you have two class hierarchies that you have no control over. So I don't really see the value of multiple dispatch in a system level programming language. Perhaps if you want to use D for an application level DSL? What are the use scenarios you guys have experience with where multiple dispatch was indispensable? Ola.
Re: how to tell if a thing is a template
On Sunday, 24 August 2014 at 00:41:36 UTC, Ellery Newcomer wrote:
Can't think off the top of my head how you do this
template IsTemplate(alias t) {
??
}
static assert(IsTemplate!IsTemplate)
__traits(compiles, is(t!X, X...))
should do it, or something similar.
Re: Why no multiple-dispatch?
On Monday, 25 August 2014 at 07:36:22 UTC, Idan Arye wrote: If multi-dispatching is done at compile-time, it can't rely on the object's runtime type - only on the static type of the reference that holds it. This is no different than regular function overloading that we already have. Well any library solution has to do this at compile-time... I assume the implementation would be similar, albeit easier because the compiler would have all the necessary information directly accessible. Are you suggesting the compiler will try to resolve the polymorphism at compile-time, looking at all possible paths that lead to a function call to check all possible runtime values it's object arguments can get? Is that not what would have to be done for a library solution in this case, anyway? Virtual methods in C can be done with GObject - though the syntax is awkward. D is so much better than C when it comes to metaprogramming, that the syntax for multimethods wouldn't be awkward(unless you consider anything that's not burned to the core syntax awkward) Of course, I understand this. What I'm saying is that while it's possible to do virtual method calls in C, the very fact that it had to be implemented so awkwardly meant that a library solution was not ideal. Now in D, the syntax is infinitely better, given. Templates and compile-time code-generation are all really good. But as I said, we have a lot of template bloat issues already. Running 3 foreach-loops at compile-time every time that template-function gets instantiated doesn't seem scalable to me... Having something like this in the compiler, which has all the required information available directly, seems like it'd be the most scalable solution.
Re: Why no multiple-dispatch?
On Monday, 25 August 2014 at 08:45:15 UTC, Ola Fosheim Grøstad wrote: However, why do you want multiple dispatch? I cannot think of any application level use scenario where you have two class hierarchies that you have no control over. So I don't really see the value of multiple dispatch in a system level programming language. Perhaps if you want to use D for an application level DSL? What are the use scenarios you guys have experience with where multiple dispatch was indispensable? Ola. Well there are a few go-to use-cases, the handling of collisions between objects in a game-engine being the most well-known (which requires Double-Dispatch). But it's basically anything that requires the Visitor Pattern, plus extra. At the end of the day, most (if not all) of the major software patterns have come about and are used due to shortfalls in the major languages. D, at least in my experience, tends to solve a lot of these shortfalls, and given that design path, why *wouldn't* we want Multiple Dispatch in the language?
unclear compile error for struct with string template
[code]
void doSome(size_t N, T, string AS)( vec!(N,T,AS) v ) { }
struct vec(size_t N, T, string AS) { T[N] data; }
void main() { doSome( vec!(3,float,xyz)([1,2,3]) ); }
[/code]
compile with new dmd v2.066.0 and get error:
Error: template opbin.doSome(ulong N, T, string AS)(vec!(N, T,
AS) v) specialization not allowed for deduced parameter AS
what does it mean?
on dmd v2.065 it worked well
code without string template parameter work well on dmd v2.066.0
[code]
void doSome(size_t N, T)( vec!(N,T) v ) { }
struct vec(size_t N, T) { T[N] data; }
void main() { doSome( vec!(3,float)([1,2,3]) ); }
[/code]
Re: unclear compile error for struct with string template
Oleg B:
[code]
void doSome(size_t N, T, string AS)( vec!(N,T,AS) v ) { }
struct vec(size_t N, T, string AS) { T[N] data; }
void main() { doSome( vec!(3,float,xyz)([1,2,3]) ); }
[/code]
compile with new dmd v2.066.0 and get error:
Error: template opbin.doSome(ulong N, T, string AS)(vec!(N, T,
AS) v) specialization not allowed for deduced parameter AS
what does it mean?
See also:
struct Vec(size_t N, T, alias string AS) {
T[N] data;
}
void doSome(size_t N, T, alias string AS)(Vec!(N, T, AS) v) {}
void main() {
auto v = Vec!(3, float, xyz)([1, 2, 3]);
doSome(v);
}
(Note that in D the names of types and structs start with an
upper case).
Bye,
bearophile
Re: unclear compile error for struct with string template
On Monday, 25 August 2014 at 11:41:28 UTC, bearophile wrote:
Oleg B:
[code]
void doSome(size_t N, T, string AS)( vec!(N,T,AS) v ) { }
struct vec(size_t N, T, string AS) { T[N] data; }
void main() { doSome( vec!(3,float,xyz)([1,2,3]) ); }
[/code]
compile with new dmd v2.066.0 and get error:
Error: template opbin.doSome(ulong N, T, string AS)(vec!(N, T,
AS) v) specialization not allowed for deduced parameter AS
what does it mean?
See also:
struct Vec(size_t N, T, alias string AS) {
T[N] data;
}
void doSome(size_t N, T, alias string AS)(Vec!(N, T, AS) v) {}
void main() {
auto v = Vec!(3, float, xyz)([1, 2, 3]);
doSome(v);
}
(Note that in D the names of types and structs start with an
upper case).
Bye,
bearophile
Does it mean that I need write alias for all arrays in template
parameters or only strings?
Re: unclear compile error for struct with string template
and when I minimal fix my libs with this issue compiler fails without any output... =( % gdb dmd (gdb) run -unittest matrix.d vector.d Starting program: /usr/bin/dmd -unittest matrix.d vector.d [Thread debugging using libthread_db enabled] Using host libthread_db library /lib64/libthread_db.so.1. [New Thread 0x77ec9700 (LWP 29224)] [Thread 0x77ec9700 (LWP 29224) exited] Program received signal SIGSEGV, Segmentation fault. 0x0046c39a in ctfeInterpret(Expression*) () (gdb) bt #0 0x0046c39a in ctfeInterpret(Expression*) () #1 0x00457012 in deduceType(RootObject*, Scope*, Type*, ArrayTemplateParameter**, ArrayRootObject**, unsigned int*, unsigned long)::DeduceType::visit(TypeInstance*) () #2 0x0044e304 in deduceType(RootObject*, Scope*, Type*, ArrayTemplateParameter**, ArrayRootObject**, unsigned int*, unsigned long) () #3 0x0045224f in deduceType(RootObject*, Scope*, Type*, ArrayTemplateParameter**, ArrayRootObject**, unsigned int*, unsigned long)::DeduceType::visit(TypeStruct*) () #4 0x00455e80 in deduceType(RootObject*, Scope*, Type*, ArrayTemplateParameter**, ArrayRootObject**, unsigned int*, unsigned long)::DeduceType::visit(Expression*) () #5 0x0044e32c in deduceType(RootObject*, Scope*, Type*, ArrayTemplateParameter**, ArrayRootObject**, unsigned int*, unsigned long) () #6 0x00458251 in TemplateDeclaration::deduceFunctionTemplateMatch(TemplateInstance*, Scope*, FuncDeclaration*, Type*, ArrayExpression**) () #7 0x0045caf1 in functionResolve(Match*, Dsymbol*, Loc, Scope*, ArrayRootObject**, Type*, ArrayExpression**)::ParamDeduce::fp(void*, Dsymbol*) () #8 0x004dd577 in overloadApply(Dsymbol*, void*, int (*)(void*, Dsymbol*)) () #9 0x0045c401 in functionResolve(Match*, Dsymbol*, Loc, Scope*, ArrayRootObject**, Type*, ArrayExpression**) () #10 0x004e0343 in resolveFuncCall(Loc, Scope*, Dsymbol*, ArrayRootObject**, Type*, ArrayExpression**, int) () #11 0x004d9522 in CallExp::semantic(Scope*) () #12 0x004eef56 in ExpInitializer::inferType(Scope*) () #13 0x004b08ad in VarDeclaration::semantic(Scope*) () #14 0x004c1f7a in DeclarationExp::semantic(Scope*) () #15 0x0043cd3b in ExpStatement::semantic(Scope*) () #16 0x004479a6 in CompoundStatement::semantic(Scope*) () #17 0x004e5e2a in FuncDeclaration::semantic3(Scope*) () #18 0x00407b28 in Module::semantic3() () #19 0x004051bc in tryMain(unsigned long, char const**) () #20 0x00338be21b45 in __libc_start_main (main=0x406e60 main, argc=4, ubp_av=0x7fffdc28, init=optimized out, fini=optimized out, rtld_fini=optimized out, stack_end=0x7fffdc18) at libc-start.c:274 #21 0x00402739 in _start ()
Re: Why no multiple-dispatch?
On Monday, 25 August 2014 at 10:16:29 UTC, Aerolite wrote: Well there are a few go-to use-cases, the handling of collisions between objects in a game-engine being the most well-known (which requires Double-Dispatch). I think a game engine is better off using a simple table or a more homogeneous engine based on properties rather than classes. You usually can assign a small integer to the relevant properties and use a 2D LUT. D, at least in my experience, tends to solve a lot of these shortfalls, and given that design path, why *wouldn't* we want Multiple Dispatch in the language? I have never had a need for it, but maybe I would have used it if it was available. I think, however, that it would fit better in Go which are going for a more dynamic implementation of interfaces without OOP. I certainly see some value in detaching virtual functions from the record definition. I believe bitC might go in that direction as well.
Compiling dll issue.
So i have been trying to follow the instructions on: http://wiki.dlang.org/Win32_DLLs_in_D but when i get to the step where i compile the dll dmd -ofmydll.dll -L/IMPLIB mydll.d dll.d mydll.def I get this output: OPTLINK (R) for Win32 Release 8.00.15 Copyright (C) Digital Mars 1989-2013 All rights reserved. http://www.digitalmars.com/ctg/optlink.html OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllGetClassObject OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllCanUnloadNow OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllRegisterServer OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllUnregisterServer OPTLINK : Error 81: Cannot EXPORT : DllCanUnloadNow OPTLINK : Error 81: Cannot EXPORT : DllGetClassObject OPTLINK : Error 81: Cannot EXPORT : DllRegisterServer OPTLINK : Error 81: Cannot EXPORT : DllUnregisterServer --- errorlevel 8 Not, very pretty. Do I have something not setup right? Im using the latest DMD as of 8/25/2014. 2.066.0 Any Ideas?
Re: Compiling dll issue.
On Monday, 25 August 2014 at 15:09:59 UTC, Taylor Hillegeist wrote: So i have been trying to follow the instructions on: http://wiki.dlang.org/Win32_DLLs_in_D but when i get to the step where i compile the dll dmd -ofmydll.dll -L/IMPLIB mydll.d dll.d mydll.def I get this output: OPTLINK (R) for Win32 Release 8.00.15 Copyright (C) Digital Mars 1989-2013 All rights reserved. http://www.digitalmars.com/ctg/optlink.html OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllGetClassObject OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllCanUnloadNow OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllRegisterServer OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllUnregisterServer OPTLINK : Error 81: Cannot EXPORT : DllCanUnloadNow OPTLINK : Error 81: Cannot EXPORT : DllGetClassObject OPTLINK : Error 81: Cannot EXPORT : DllRegisterServer OPTLINK : Error 81: Cannot EXPORT : DllUnregisterServer --- errorlevel 8 Not, very pretty. Do I have something not setup right? Im using the latest DMD as of 8/25/2014. 2.066.0 Any Ideas? So, I figured it out! I used the wrong example for mydll.def. - LIBRARY MYDLL DESCRIPTION 'My DLL written in D' EXETYPE NT CODEPRELOAD DISCARDABLE DATAWRITE EXPORTS DllGetClassObject @2 DllCanUnloadNow @3 DllRegisterServer @4 DllUnregisterServer @5 -- The above will cause errors: even though it makes you think that it should be mydll.def it is not. -- LIBRARY mydll.dll EXETYPE NT SUBSYSTEM WINDOWS CODE SHARED EXECUTE DATA WRITE -- The above is the correct .def contents Thanks all!
Re: Compiling dll issue.
On Monday, 25 August 2014 at 15:09:59 UTC, Taylor Hillegeist wrote: So i have been trying to follow the instructions on: http://wiki.dlang.org/Win32_DLLs_in_D but when i get to the step where i compile the dll dmd -ofmydll.dll -L/IMPLIB mydll.d dll.d mydll.def I get this output: OPTLINK (R) for Win32 Release 8.00.15 Copyright (C) Digital Mars 1989-2013 All rights reserved. http://www.digitalmars.com/ctg/optlink.html OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllGetClassObject OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllCanUnloadNow OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllRegisterServer OPTLINK : Error 180: No Match Found for Export/ENTRY - : DllUnregisterServer OPTLINK : Error 81: Cannot EXPORT : DllCanUnloadNow OPTLINK : Error 81: Cannot EXPORT : DllGetClassObject OPTLINK : Error 81: Cannot EXPORT : DllRegisterServer OPTLINK : Error 81: Cannot EXPORT : DllUnregisterServer --- errorlevel 8 Not, very pretty. Do I have something not setup right? Im using the latest DMD as of 8/25/2014. 2.066.0 Any Ideas? If you don't use the extern(C) foreign function interface then the name won't match to the export name as written in the source (in the binary you'll get the bytecount of all the param size with a @ before). si you need to create a name table for optlink (http://www.digitalmars.com/ctg/ctgDefFiles.html) (http://www.digitalmars.com/archives/cplusplus/4029.html)
Error with constraints on a templated fuction
I've done things like this before with traits and I figured that
this way should work as well, but it gives me errors instead.
Perhaps someone can point out my flaws.
immutable(T)[] toString(T)(const(T)* str)
if(typeof(T) is dchar)//this is where the error is
{
return str[0..strlen(str)].idup; //I have strlen defined for
each *string
}
I was going to add some || sections for the other string types,
but this one won't even compile.
src/dsfml/system/string.d(34): Error: found ')' when expecting
'.' following dchar
src/dsfml/system/string.d(35): Error: found '{' when expecting
identifier following 'dchar.'
src/dsfml/system/string.d(36): Error: found 'return' when
expecting ')'
src/dsfml/system/string.d(36): Error: semicolon expected
following function declaration
src/dsfml/system/string.d(36): Error: no identifier for
declarator str[0 .. strlen(str)]
src/dsfml/system/string.d(36): Error: no identifier for
declarator .idup
src/dsfml/system/string.d(37): Error: unrecognized declaration
It compiles if I remove the 'if(typeof(T) is dchar)' section. Any
thoughts?
Re: Error with constraints on a templated fuction
Jeremy DeHaan: It compiles if I remove the 'if(typeof(T) is dchar)' section. Any thoughts? Try: if (is(T == dchar)) Bye, bearophile
Re: Error with constraints on a templated fuction
On Mon, 25 Aug 2014 15:48:10 + Jeremy DeHaan via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: It compiles if I remove the 'if(typeof(T) is dchar)' section. Any thoughts? is should be used as function. here. i.e.: `if (is(T == dchar))` signature.asc Description: PGP signature
Re: Error with constraints on a templated fuction
On Monday, 25 August 2014 at 15:59:38 UTC, ketmar via Digitalmars-d-learn wrote: On Mon, 25 Aug 2014 15:48:10 + Jeremy DeHaan via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: It compiles if I remove the 'if(typeof(T) is dchar)' section. Any thoughts? is should be used as function. here. i.e.: `if (is(T == dchar))` Is its ability to be used as a function like this documented anywhere? I looked and could not find it.
Re: Error with constraints on a templated fuction
On Monday, 25 August 2014 at 15:52:20 UTC, bearophile wrote: Jeremy DeHaan: It compiles if I remove the 'if(typeof(T) is dchar)' section. Any thoughts? Try: if (is(T == dchar)) Bye, bearophile That one compiles, and I'm assuming it works. I didn't know you could use is this way. I've only seen it as an 'obj1 is obj2' sort of way. Thanks much!
Re: Error with constraints on a templated fuction
On Mon, 25 Aug 2014 16:11:27 + Jeremy DeHaan via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Is its ability to be used as a function like this documented anywhere? I looked and could not find it. http://dlang.org/concepts.html template constraints is a special case. is not a real function here, it's more like special predicate syntax. signature.asc Description: PGP signature
Re: Error with constraints on a templated fuction
On Monday, 25 August 2014 at 16:20:24 UTC, ketmar via Digitalmars-d-learn wrote: On Mon, 25 Aug 2014 16:11:27 + Jeremy DeHaan via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Is its ability to be used as a function like this documented anywhere? I looked and could not find it. http://dlang.org/concepts.html template constraints is a special case. is not a real function here, it's more like special predicate syntax. Awesome! Thanks so much.
Learning D
Me: Software developer for 30 years. So perhaps this is old fashion, but I wanted to start using D by whipping together nice little personal utilities. I tried installing MonoDevelop and Mono-D. I can't even figure out the basics, such as adding references to a project. There are no options in the context menus, and although it looks like drag an drop might work (a '+' sign appears by the cursor), dropping a file from the filesystem doesn't work either. Although I dream of someday being able to add a reference to a project, I'm not really sure what I might drag in. I managed to download and compile GtkD, since it seems like a GUI would be a nice place to start (again, old fashion). I got three *.lib files out of it... H... Maybe these are references?? I had installed the Visual Studio plugin, but I don't want to use this since I would like to eventually migrate away from Windows. Let me cut to the chase. I have no friggin' clue how to start, and I can't seem to find a tutorial anywhere... What IDE should I use? I'm not big fan of Eclipse, although if I had to use it this wouldn't be a dealbreaker. Give me something easy and lightweight, unless you've got a GUI builder (this is why I started with MonoDevelop, though this isn't working so well for me). What Widget library should I use? I started with GTKD, but since there are no tutorials does this mean nobody actually does this? Should I use DWT? What about QT? I just want something simple and mainstream to start learning D with. Any thoughts?
Re: Error with constraints on a templated fuction
On Mon, 25 Aug 2014 15:48:10 +
Jeremy DeHaan via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com wrote:
I've done things like this before with traits and I figured that
this way should work as well, but it gives me errors instead.
Perhaps someone can point out my flaws.
immutable(T)[] toString(T)(const(T)* str)
if(typeof(T) is dchar)//this is where the error is
{
return str[0..strlen(str)].idup; //I have strlen defined for
each *string
}
I was going to add some || sections for the other string types,
but this one won't even compile.
src/dsfml/system/string.d(34): Error: found ')' when expecting
'.' following dchar
src/dsfml/system/string.d(35): Error: found '{' when expecting
identifier following 'dchar.'
src/dsfml/system/string.d(36): Error: found 'return' when
expecting ')'
src/dsfml/system/string.d(36): Error: semicolon expected
following function declaration
src/dsfml/system/string.d(36): Error: no identifier for
declarator str[0 .. strlen(str)]
src/dsfml/system/string.d(36): Error: no identifier for
declarator .idup
src/dsfml/system/string.d(37): Error: unrecognized declaration
It compiles if I remove the 'if(typeof(T) is dchar)' section. Any
thoughts?
As the others have pointed out, you need to do is(T == dchar). The way you
used is the is operator and it checks for bitwise equality (most frequently
used for comparing pointers), and it's a runtime operation, whereas the is
that you need to use in a template constraint is an is expression, which is a
compile time operation:
http://dlang.org/expression.html#IsExpression
is expressions actually get pretty complicated in their various forms, but the
most basic two are probably is(T == dchar), which checks that the two types ar
the same, and is(T : dchar), which checks that T implictly converts to dchar.
Another commonly used one is is(typeof(foo)). typeof(foo) gets the type of foo
and will result in void if foo doesn't exist, and is(void) is false, whereas
is(someOtherType) is true, so it's frequently used to check whether something
is valid. The Phobos source code is littered with examples (especially in
std.algorithm, std.range, and std.traits), since is expressions are frequently
used in template constraints.
- Jonathan M Davis
Re: Learning D
On Monday, 25 August 2014 at 16:46:11 UTC, Ryan wrote: Me: Software developer for 30 years. So perhaps this is old fashion, but I wanted to start using D by whipping together nice little personal utilities. I tried installing MonoDevelop and Mono-D. I can't even figure out the basics, such as adding references to a project. There are no options in the context menus, and although it looks like drag an drop might work (a '+' sign appears by the cursor), dropping a file from the filesystem doesn't work either. Although I dream of someday being able to add a reference to a project, I'm not really sure what I might drag in. I managed to download and compile GtkD, since it seems like a GUI would be a nice place to start (again, old fashion). I got three *.lib files out of it... H... Maybe these are references?? I had installed the Visual Studio plugin, but I don't want to use this since I would like to eventually migrate away from Windows. Let me cut to the chase. I have no friggin' clue how to start, and I can't seem to find a tutorial anywhere... What IDE should I use? I'm not big fan of Eclipse, although if I had to use it this wouldn't be a dealbreaker. Give me something easy and lightweight, unless you've got a GUI builder (this is why I started with MonoDevelop, though this isn't working so well for me). What Widget library should I use? I started with GTKD, but since there are no tutorials does this mean nobody actually does this? Should I use DWT? What about QT? I just want something simple and mainstream to start learning D with. Any thoughts? Mono-D + dub (see code.dlang.org) is the easiest way to get things working quickly. Mono-D has builtin support for dub. For learning D, see Ali's book: http://ddili.org/ders/d.en/index.html (from scratch) or Andrei's The D Programming Language (for the more experienced). Adam D. Ruppe's D Cookbook also has interesting examples of usage.
Re: Error with constraints on a templated fuction
On Mon, Aug 25, 2014 at 03:48:10PM +, Jeremy DeHaan via Digitalmars-d-learn wrote: I've done things like this before with traits and I figured that this way should work as well, but it gives me errors instead. Perhaps someone can point out my flaws. immutable(T)[] toString(T)(const(T)* str) if(typeof(T) is dchar)//this is where the error is The correct syntax is: if (is(typeof(T) == dchar)) When comparing two values for equality (i.e., are these two values equal to each other), use if (a == b). When comparing two variables for identity (i.e., do these two references point to the same data), use if (a is b). When comparing two types, use is(A == B). T -- Verbing weirds language. -- Calvin ( Hobbes)
Re: Learning D
On Monday, 25 August 2014 at 16:46:11 UTC, Ryan wrote: Me: Software developer for 30 years. So perhaps this is old fashion, but I wanted to start using D by whipping together nice little personal utilities. I tried installing MonoDevelop and Mono-D. I can't even figure out the basics, such as adding references to a project. There are no options in the context menus, and although it looks like drag an drop might work (a '+' sign appears by the cursor), dropping a file from the filesystem doesn't work either. Although I dream of someday being able to add a reference to a project, I'm not really sure what I might drag in. I managed to download and compile GtkD, since it seems like a GUI would be a nice place to start (again, old fashion). I got three *.lib files out of it... H... Maybe these are references?? I had installed the Visual Studio plugin, but I don't want to use this since I would like to eventually migrate away from Windows. Let me cut to the chase. I have no friggin' clue how to start, and I can't seem to find a tutorial anywhere... What IDE should I use? I'm not big fan of Eclipse, although if I had to use it this wouldn't be a dealbreaker. Give me something easy and lightweight, unless you've got a GUI builder (this is why I started with MonoDevelop, though this isn't working so well for me). What Widget library should I use? I started with GTKD, but since there are no tutorials does this mean nobody actually does this? Should I use DWT? What about QT? I just want something simple and mainstream to start learning D with. Any thoughts? I don't use an IDE, but MonoD seems to be the most recommended cross-platform option. It has a wiki page here if it helps: http://wiki.dlang.org/Mono-D I recommend only using an IDE that uses DUB (http://code.dlang.org/about), which is becoming the de facto standard for building D projects, and is cross-IDE, allowing you to move between IDEs and to work with developers using other IDEs. MonoD probably uses this, as does DDT(Eclipse). I have no idea what interface MonoD or other IDEs offer for DUB, but DUB uses a 'dub.json' file where you specify libraries you use and their versions. DUB will automatically download the libraries when you compile the project. Available DUB packages (libraries/apps) are listed at http://code.dlang.org . That is probably also the best list of D libs we have at the moment, although many projects are not there yet. Only use DWT if you like Java-style code. QtD is not in usable state yet. GtkD should be good, better for 'big' apps (i.e. more features), TkD for simple ones (simpler to use). To learn about the language itself, this (free) book is really good: http://ddili.org/ders/d.en/index.html
Re: Error with constraints on a templated fuction
On Monday, 25 August 2014 at 17:05:48 UTC, H. S. Teoh via Digitalmars-d-learn wrote: On Mon, Aug 25, 2014 at 03:48:10PM +, Jeremy DeHaan via Digitalmars-d-learn wrote: I've done things like this before with traits and I figured that this way should work as well, but it gives me errors instead. Perhaps someone can point out my flaws. immutable(T)[] toString(T)(const(T)* str) if(typeof(T) is dchar)//this is where the error is The correct syntax is: if (is(typeof(T) == dchar)) Almost... T is already a type; typeof(T) doesn't compile.
Using the delete Keyword /w GC
People have been saying for quite a long time not to use the `delete` keyword on GC-allocated pointers. I've looked extensively through the code inside the engine and even made a few modifications on it/benchmarked it for weeks and I still can't see why it would be wrong. Wouldn't it help avoid collections and make a good hybrid of manual management/collected code? The free lists in the GC engine look quite convenient to use. Any ideas?
Re: Why no multiple-dispatch?
On Monday, 25 August 2014 at 10:02:41 UTC, Aerolite wrote: On Monday, 25 August 2014 at 07:36:22 UTC, Idan Arye wrote: If multi-dispatching is done at compile-time, it can't rely on the object's runtime type - only on the static type of the reference that holds it. This is no different than regular function overloading that we already have. Well any library solution has to do this at compile-time... I assume the implementation would be similar, albeit easier because the compiler would have all the necessary information directly accessible. This CAN NOT BE DONE at compile-time, since the compiler doesn't know at compile time the exact subclass of the instance it'll get at runtime. To clarify: I'm not talking about the creation of the multi-method mechanism - which *can* be done at compile-time - I'm talking about invoking that mechanism to determine which overload to call, and this can only be done at runtime. Are you suggesting the compiler will try to resolve the polymorphism at compile-time, looking at all possible paths that lead to a function call to check all possible runtime values it's object arguments can get? Is that not what would have to be done for a library solution in this case, anyway? If you look back, you'll notice this argument(and the two before it) was not against multi-methods at the language level - it was about multi-methods by default. If they are optional, instantiating all the overloads will only happen when it's used, so it won't be that bad. Virtual methods in C can be done with GObject - though the syntax is awkward. D is so much better than C when it comes to metaprogramming, that the syntax for multimethods wouldn't be awkward(unless you consider anything that's not burned to the core syntax awkward) Of course, I understand this. What I'm saying is that while it's possible to do virtual method calls in C, the very fact that it had to be implemented so awkwardly meant that a library solution was not ideal. Now in D, the syntax is infinitely better, given. Templates and compile-time code-generation are all really good. But as I said, we have a lot of template bloat issues already. Running 3 foreach-loops at compile-time every time that template-function gets instantiated doesn't seem scalable to me... Having something like this in the compiler, which has all the required information available directly, seems like it'd be the most scalable solution. No one is trying to claim that a library implementation will be superior to a language-level solution in terms of speed, memory usage, binary size, compilation speed or syntax elegance. Language-level solutions can usually achieve better results in these regards. The problem is that they come with a price: * External tools needs to be modified to work with them. * Alternative implementations need to implement them(even though the frontend is shared, there can always be some complications(plus I think mutli-methods might need some backend modifications as well, thhoguh I'm no expert on that matter)) * Risking regressions - changing the code will never be as orthogonal as changing the data it works on... The point is that the usefulness of multi-methods, and the inconvenience of having as a library solution are not nearly big enough to pay that price.
Re: Using the delete Keyword /w GC
On Monday, 25 August 2014 at 17:10:11 UTC, Etienne wrote: People have been saying for quite a long time not to use the `delete` keyword on GC-allocated pointers. I've looked extensively through the code inside the engine and even made a few modifications on it/benchmarked it for weeks and I still can't see why it would be wrong. Wouldn't it help avoid collections and make a good hybrid of manual management/collected code? The free lists in the GC engine look quite convenient to use. Any ideas? delete was deprecated because it is memory unsafe (there may still be references to the memory). You can still use GC.free() to free the memory but it must only be used with care. I feel if you are managing delete yourself you might as well manage allocation yourself too and take pressure off the GC. If you are sure you have only one reference and GC.free() is safe, Unique was probably a better choice anyway.
Re: Why no multiple-dispatch?
On Monday, 25 August 2014 at 17:16:10 UTC, Idan Arye wrote:
* Alternative implementations need to implement them(even
though the frontend is shared, there can always be some
complications(plus I think mutli-methods might need some
backend modifications as well, thhoguh I'm no expert on that
matter))
* Risking regressions - changing the code will never be as
orthogonal as changing the data it works on...
The point is that the usefulness of multi-methods, and the
inconvenience of having as a library solution are not nearly
big enough to pay that price.
If we assume just double-dispatch over class-types and that you
instantiate all functions first. Couldn't you then have this:
eat(virtual BaseBeing v, virtual BaseFood f,float amount){}
eat(virtual Human v, virtual Fruit f,float amount){]
eat(virtual Human v, virtual Stone f,float amount){}
eat(virtual Monster v, virtual Corpse f,float amount){}
eat(virtual Human v, virtual Corpse f,float amount){}
Then extend the typeinfo of classes in the first param with a
minimal typeid and 2D table that lists all combinations that the
custom linker can find based on the mangling?
Or maybe there are some hidden traps…
Re: Why no multiple-dispatch?
On Monday, 25 August 2014 at 17:28:45 UTC, Ola Fosheim Grøstad wrote: Then extend the typeinfo of classes in the first param with a minimal typeid and 2D table that lists all combinations that the custom linker can find based on the mangling? Maybe it would be better to put in the restriction that all double-dispatch functions with the same name are located in the same file.
Re: Error with constraints on a templated fuction
On Mon, Aug 25, 2014 at 05:10:18PM +, via Digitalmars-d-learn wrote: On Monday, 25 August 2014 at 17:05:48 UTC, H. S. Teoh via Digitalmars-d-learn wrote: On Mon, Aug 25, 2014 at 03:48:10PM +, Jeremy DeHaan via Digitalmars-d-learn wrote: I've done things like this before with traits and I figured that this way should work as well, but it gives me errors instead. Perhaps someone can point out my flaws. immutable(T)[] toString(T)(const(T)* str) if(typeof(T) is dchar)//this is where the error is The correct syntax is: if (is(typeof(T) == dchar)) Almost... T is already a type; typeof(T) doesn't compile. Ah, right, it should be simply: if (is(T == dchar)) Should've read more carefully before replying. :-P T -- It only takes one twig to burn down a forest.
Re: Error with constraints on a templated fuction
On 08/25/14 18:52, Jonathan M Davis via Digitalmars-d-learn wrote: Another commonly used one is is(typeof(foo)). typeof(foo) gets the type of foo and will result in void if foo doesn't exist, and is(void) is false, whereas D is not quite that simple. ;) static assert(is(void)==true); (a) `typeof(invalid)` is an error; (b) the `is(...)` expression swallows errors; hence (a)+(b) - static assert(is(typeof(invalid))==false); artur
Re: Learning D
Thanks for both responses. This is the information I was looking for. I have DMD, GTK# (For MonoDevelop), MonoDevelop, MonoD, dubs, and GTKD installed. I've got some things to compile... So the crux of my issue is that I can't figure out how to link lib files in MonoDevelop. I wonder if there is a problem in the latest version or something.
Re: Learning D
Anyone know MonoDevelop? Why is the Edit References context menu item missing. I have it at the top (Project-Edit References...) but when I click it nothing happens. Grrr.
Is this a bug when creating proxies in classes?
Compiling the following code:
import std.typecons;
class Foo
{
private int foo;
mixin Proxy!(foo);
this(int x)
{
this.foo = x;
}
}
void main()
{
}
Produces this error:
:!rdmd --force -de -debug -w test.d
/usr/include/dmd/phobos/std/typecons.d(4043): Error: template
instance isArray!(typeof(a)) template 'isArray' is not defined
test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating
Failed: [dmd, -de, -debug, -w, -v, -o-, test.d,
-I.]
Can anyone else confirm or am i doing something wrong. I'm using
DMD 2.066.0 64bit Ubuntu 14.04.
Re: Learning D
On Monday, 25 August 2014 at 17:57:54 UTC, Ryan wrote: Anyone know MonoDevelop? Why is the Edit References context menu item missing. I have it at the top (Project-Edit References...) but when I click it nothing happens. Grrr. I couldnt figure it out either tbh (creating dub projects using MonoD) I just fire up a command line, go to my workspace folder, and do dub init project name here Then, in monoD, File - Open - C:\Path\To\Project\dub.json Then your good to go regarding MonoD.
Re: Is this a bug when creating proxies in classes?
On 08/25/2014 11:10 AM, Gary Willoughby wrote:
Compiling the following code:
import std.typecons;
class Foo
{
private int foo;
mixin Proxy!(foo);
this(int x)
{
this.foo = x;
}
}
void main()
{
}
Produces this error:
:!rdmd --force -de -debug -w test.d
/usr/include/dmd/phobos/std/typecons.d(4043): Error: template instance
isArray!(typeof(a)) template 'isArray' is not defined
test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating
Failed: [dmd, -de, -debug, -w, -v, -o-, test.d, -I.]
Can anyone else confirm or am i doing something wrong. I'm using DMD
2.066.0 64bit Ubuntu 14.04.
isArray is defined in std.traits. I don't know why it doesn't work even
though std.typecons does import it.
The workaround is to import it yourself in your program:
import std.traits;
Ali
Re: Is this a bug when creating proxies in classes?
On Monday, 25 August 2014 at 18:10:33 UTC, Gary Willoughby wrote: :!rdmd --force -de -debug -w test.d /usr/include/dmd/phobos/std/typecons.d(4043): Error: template instance isArray!(typeof(a)) template 'isArray' is not defined test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating Failed: [dmd, -de, -debug, -w, -v, -o-, test.d, -I.] Can anyone else confirm or am i doing something wrong. I'm using DMD 2.066.0 64bit Ubuntu 14.04. It stopped working after this PR was merged: https://github.com/D-Programming-Language/phobos/pull/1899 But I suspect that something else is going on. The PR only introduced the call to `isArray` into `std.typecons.Proxy`.
Re: Is this a bug when creating proxies in classes?
On 08/25/2014 11:38 AM, Marc Schütz schue...@gmx.net wrote: On Monday, 25 August 2014 at 18:10:33 UTC, Gary Willoughby wrote: :!rdmd --force -de -debug -w test.d /usr/include/dmd/phobos/std/typecons.d(4043): Error: template instance isArray!(typeof(a)) template 'isArray' is not defined test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating Failed: [dmd, -de, -debug, -w, -v, -o-, test.d, -I.] Can anyone else confirm or am i doing something wrong. I'm using DMD 2.066.0 64bit Ubuntu 14.04. It stopped working after this PR was merged: https://github.com/D-Programming-Language/phobos/pull/1899 But I suspect that something else is going on. The PR only introduced the call to `isArray` into `std.typecons.Proxy`. It can be explained if the mixed-in template is evaluated at the mixin context without bringing in the imported modules to that context. I don't know whether it is true or whether it is a known limitation. Ali
Re: Is this a bug when creating proxies in classes?
On Monday, 25 August 2014 at 18:44:36 UTC, Ali Çehreli wrote: It can be explained if the mixed-in template is evaluated at the mixin context without bringing in the imported modules to that context. I don't know whether it is true or whether it is a known limitation. You're right, that's it! It works when I import std.traits first. So... the fix is to import std.traits inside template Proxy. Going to submit a PR.
Re: Is this a bug when creating proxies in classes?
On Monday, 25 August 2014 at 19:12:48 UTC, Marc Schütz wrote: On Monday, 25 August 2014 at 18:44:36 UTC, Ali Çehreli wrote: It can be explained if the mixed-in template is evaluated at the mixin context without bringing in the imported modules to that context. I don't know whether it is true or whether it is a known limitation. You're right, that's it! It works when I import std.traits first. So... the fix is to import std.traits inside template Proxy. Going to submit a PR. https://github.com/D-Programming-Language/phobos/pull/2463
Re: Using the delete Keyword /w GC
On Monday, 25 August 2014 at 17:20:20 UTC, Brad Anderson wrote: On Monday, 25 August 2014 at 17:10:11 UTC, Etienne wrote: People have been saying for quite a long time not to use the `delete` keyword on GC-allocated pointers. I've looked extensively through the code inside the engine and even made a few modifications on it/benchmarked it for weeks and I still can't see why it would be wrong. Wouldn't it help avoid collections and make a good hybrid of manual management/collected code? The free lists in the GC engine look quite convenient to use. Any ideas? delete was deprecated because it is memory unsafe (there may still be references to the memory). You can still use GC.free() to free the memory but it must only be used with care. I feel if you are managing delete yourself you might as well manage allocation yourself too and take pressure off the GC. If you are sure you have only one reference and GC.free() is safe, Unique was probably a better choice anyway. Actually, delete hasn't technically been deprecated yet even though it was supposed to be, which is part of the problem. If it were, presumably folks would stop using it. But yeah, the key problem is that deleting GCed memory is inherently unsafe. You can get away with it if you know for sure that there are no other references to that object, but if you screw it up, nasty things will happen. Normally, using the GC is supposed to guarantee memory safety, and freeing GC memory yourself negates that. And as you point out, you really don't gain much by using the GC if you're going to be deleting stuff yourself. At that point, you might as well be managing the memory yourself. The main impediment there is the fact that we don't currently have a nice way to construct objects on the heap without new. After the memory is malloced, you need to use emplace to construct the object in that memory, and that gets complicated. However, once we have the custom allocators, that problem should go away, because then we should be able to do something like auto foo = alloc.foo!Foo(arg1, arg2); and all of the emplace pain will be dealt with for you. So, until we have that, I can see why someone would want to use delete, but it's inherently unsafe, and we really need to get it deprecated and then removed. - Jonathan M Davis
Re: Learning D
On Monday, 25 August 2014 at 18:12:25 UTC, Colin wrote: On Monday, 25 August 2014 at 17:57:54 UTC, Ryan wrote: Anyone know MonoDevelop? Why is the Edit References context menu item missing. I have it at the top (Project-Edit References...) but when I click it nothing happens. Grrr. I couldnt figure it out either tbh (creating dub projects using MonoD) I just fire up a command line, go to my workspace folder, and do dub init project name here Then, in monoD, File - Open - C:\Path\To\Project\dub.json Then your good to go regarding MonoD. Yeah, I gave up on MonoD to try and figure out what is going on behind the scenes by compiling with text files... I had a little success compiling, followed by a failure to run because I don't have the right version of GTK+ on my system... Then I thought I'd learn dub. Well, this is NOT going well... I did a git clone of gtk-d, then tried to build with dub (renamed the package.json to dub.json), and it told me Conflicting package multi-reference I have no clue and I've tried removing package references I tried dub remove gtk-d --version=* but it just lists out excuses why it can't work... no retrieval journal found for..., Untracked file found So then I try every variation of dub remove-local and dub remove-path I can think of. I give up. Why not just have a dub -IFuckedUpSoLetsStartOverCleanSlated option?
Cross-module inlining with separate compilation?
Is there a way to have cross-module inlining but with separate compilation? Like with link-time generation in C++ compilers.
Getting RefCounted to work with classes
Hello,
the code below compiles and runs fine. However, when I change
Payload from struct to class I get compiler errors:
Error 1 Error: template instance
std.typecons.RefCounted!(Payload,
cast(RefCountedAutoInitialize)1) does not match template
declaration RefCounted(T, RefCountedAutoInitialize autoInit =
RefCountedAutoInitialize.yes) if (!is(T ==
class)) C:\Users\Nutzer\Windows Ordner\Documents\Visual Studio
2013\Projects\RefCountedScratch\RefCountedScratch\main.d 26
I tried many things, but nothing did it. Any help appreciated :-).
Thanks, Bienlein
import std.stdio;
import std.typecons;
struct Payload
{
private int num = 0;
this(int i)
{
num = i;
writefln(Payload's constructor called);
}
~this()
{
writefln(Payload's destructor called);
}
}
int main(string[] argv)
{
alias RefCounted!(Payload, RefCountedAutoInitialize.yes) Data;
int bar = 12;
Data data = Data(bar);
return 0;
}
Re: Is this a bug when creating proxies in classes?
On 08/25/2014 12:17 PM, Marc Schütz schue...@gmx.net wrote: On Monday, 25 August 2014 at 19:12:48 UTC, Marc Schütz wrote: On Monday, 25 August 2014 at 18:44:36 UTC, Ali Çehreli wrote: It can be explained if the mixed-in template is evaluated at the mixin context without bringing in the imported modules to that context. I don't know whether it is true or whether it is a known limitation. You're right, that's it! It works when I import std.traits first. So... the fix is to import std.traits inside template Proxy. Going to submit a PR. https://github.com/D-Programming-Language/phobos/pull/2463 Thanks! And I learned from you in the pull request the following fact: quote Quoting http://dlang.org/template-mixin : Unlike a template instantiation, a template mixin's body is evaluated within the scope where the mixin appears, not where the template declaration is defined. It is analogous to cutting and pasting the body of the template into the location of the mixin. /quote Ali
Re: D1: Error: duplicate union initialization for size
Ok, let's try something simpler... Where can I find the D1
v1.076 compiler error meaning of,
Error: duplicate union initialization for size
for this line,
const Size DEFAULT_SCALE = { 5, 13 };
thanks.
Re: Using the delete Keyword /w GC
On Monday, 25 August 2014 at 17:10:11 UTC, Etienne wrote: People have been saying for quite a long time not to use the `delete` keyword on GC-allocated pointers. I've looked extensively through the code inside the engine and even made a few modifications on it/benchmarked it for weeks and I still can't see why it would be wrong. Wouldn't it help avoid collections and make a good hybrid of manual management/collected code? The free lists in the GC engine look quite convenient to use. Any ideas? Until custom class de/allocators are not really deprecated, the delete keyword is not necessarly deleting from the GC. Look at this: http://wiki.dlang.org/Memory_Management#Explicit_Class_Instance_Allocation You can do the same but without adding the class reference to the GC. Then delete will call the custom deallocator which is itself not calling the GC. So in a way I think you're right when you say that delete could help into manual mem managment. But that's not a reliable (over time) situation.
Re: Learning D
On Monday, 25 August 2014 at 20:37:16 UTC, Ryan wrote: Then I thought I'd learn dub. Well, this is NOT going well... I did a git clone of gtk-d, then tried to build with dub (renamed the package.json to dub.json), and it told me Conflicting package multi-reference I have no clue and I've tried removing package references I tried dub remove gtk-d --version=* but it just lists out excuses why it can't work... no retrieval journal found for..., Untracked file found Why you try removing from dub something you have manually cloned? It is not even aware of local gtk-d copy if you just cloned with registering local path. Expected approach is to create a new dub project and add gtk-d to dependencies - rest is up to how well-maintained gtk-d itself is.
Re: Are there any exercises/challenges for D?
On Sunday, 24 August 2014 at 23:20:21 UTC, maik klein wrote:
On Sunday, 24 August 2014 at 21:51:39 UTC, Weaseldog wrote:
On Sunday, 24 August 2014 at 20:32:02 UTC, maik klein wrote:
Are there any exercises/challenges for D?
Something like this?
http://www.haskell.org/haskellwiki/99_questions/1_to_10
Well, you could port 99 lisp problems to D - D can be written
in a fairly functional style ;)
I am just trying to learn D by writing code. Of course I could
just do them in D but I would like to compare my version with
idiomatic D.
It's actually quite strange that no one has done something like
this in D, it's usually the first thing people do.
Have you heard of Project Euler? https://projecteuler.net/
The problems are mostly mathematical, and once you answer you can
compare your solution to the other solutions people have written
in other languages. The early questions also have some very
unique and beautiful range-based D solutions.
import std.algorithm;
import std.range;
import std.stdio;
alias fold = std.functional.binaryReverseArgs!(reduce!((n1, n2)
= n1 + n2));
enum limit = 4_000_000;
void main()
{
recurrence!q{a[n-1] + a[n-2]}(1, 1)
.take(1000)
.filter!(n = n = 0 n limit n % 2 == 0)
.sum.writeln;
}
Re: Are there any exercises/challenges for D?
On Tuesday, 26 August 2014 at 01:57:06 UTC, Meta wrote:
Have you heard of Project Euler? https://projecteuler.net/
The problems are mostly mathematical, and once you answer you
can compare your solution to the other solutions people have
written in other languages. The early questions also have some
very unique and beautiful range-based D solutions.
import std.algorithm;
import std.range;
import std.stdio;
alias fold = std.functional.binaryReverseArgs!(reduce!((n1, n2)
= n1 + n2));
enum limit = 4_000_000;
void main()
{
recurrence!q{a[n-1] + a[n-2]}(1, 1)
.take(1000)
.filter!(n = n = 0 n limit n % 2 == 0)
.sum.writeln;
}
Whoops, wrong code. Also, this is the answer to PE problem 2.
import std.algorithm;
import std.range;
import std.stdio;
enum limit = 4_000_000;
void main()
{
recurrence!q{a[n-1] + a[n-2]}(1, 1)
.take(1000)
.filter!(n = n = 0 n limit n % 2 == 0)
.sum
.writeln;
}
Re: Learning D
Not sure how up your alley this is, but vim support for D is excellent.
Re: Learning D
On Tue, Aug 26, 2014 at 02:13:04AM +, Weaseldog via Digitalmars-d-learn wrote: Not sure how up your alley this is, but vim support for D is excellent. I use vim for D. T -- War doesn't prove who's right, just who's left. -- BSD Games' Fortune
Casting to union type?
Is it possible to allow implicit casting from a base type to a
union type? For example, considering the following basic vector
union:
union vec2 {
struct {
float x = 0.0f;
float y = 0.0f;
}
float[2] v;
enum length = v.length;
ref auto opIndex(size_t idx) {
assert(idx = 0 idx length, Bounds error on index);
return v[idx];
}
auto opAssign(float[] f) {
assert(f.length == length, Bounds error on assignment);
v[0..length] = f[0..length];
return this;
}
}
vec2 a = vec2(1.0, 2.0); // fine
vec2 b;
b = [3.0, 4.0]; //fine
vec2 c = [5.0, 6.0]; // cannot cast float[] to vec2
Overloading opCast() seems to be only for outbound casting, and
unions can't have this() constructors like structs. Is there any
way to accomplish this?
Re: Casting to union type?
On Tuesday, 26 August 2014 at 02:33:25 UTC, cc wrote: Is it possible to allow implicit casting from a base type to a union type? All implict conversions are done using alias this: http://dlang.org/class.html#AliasThis - Jonathan M Davis
Re: Cross-module inlining with separate compilation?
On Mon, 25 Aug 2014 21:07:06 + ponce via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Is there a way to have cross-module inlining but with separate compilation? Like with link-time generation in C++ compilers. i think that turning your functions into templates should do the trick. i.e. int myfunc (int n) -- int myfunc() (int n). but this is a hack, of course. signature.asc Description: PGP signature
Re: Cross-module inlining with separate compilation?
On Tuesday, 26 August 2014 at 04:34:39 UTC, ketmar via Digitalmars-d-learn wrote: On Mon, 25 Aug 2014 21:07:06 + ponce via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Is there a way to have cross-module inlining but with separate compilation? Like with link-time generation in C++ compilers. i think that turning your functions into templates should do the trick. i.e. int myfunc (int n) -- int myfunc() (int n). but this is a hack, of course. No template hack needed now. https://issues.dlang.org/show_bug.cgi?id=10985
Re: Cross-module inlining with separate compilation?
On Tue, 26 Aug 2014 04:49:17 + hane via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: No template hack needed now. unless you using gdc, for example. ;-) signature.asc Description: PGP signature
