Re: What am I doing wrong here?
On Saturday, 7 May 2022 at 02:29:59 UTC, Salih Dincer wrote:
On Friday, 6 May 2022 at 18:04:13 UTC, JG wrote:
```d
//...
struct Adder {
int a;
int opCall(int b) { return a+b; }
}
auto adder(int a) {
auto ret = Adder.init;
ret.a=a;
return ret;
}
void main() {
auto g = adder(5);
g(5).writeln; // 10
auto d = toDelegate!(int, int)(g);
d(5).writeln; // 10
// ...
}
```
The value returned by the delegate structure in the above line
is 10. Its parameter is 5, but if you do it to 21, you will get
42. So it doesn't have the ability to delegate Adder.
In summary, the sum function isn't executing. Instead, its
value gets double.
SDB@79
What do you mean?
```d
import std;
struct Delegate(A,B) {
B function(void* ptr, A a) f;
void* data;
B opCall(A a) {
return f(data,a);
}
}
auto toDelegate(A, B,S)(ref S s) {
static B f(void* ptr, A a) {
return (*(cast(S*) ptr))(a);
}
Delegate!(A,B) ret;
ret.f=
ret.data= cast(void*)
return ret;
}
struct Adder {
int a;
int opCall(int b) { return a+b; }
}
auto adder(int a) {
auto ret = Adder.init;
ret.a=a;
return ret;
}
void main() {
auto g = adder(5);
g(5).writeln;
auto d = toDelegate!(int, int)(g);
d(41).writeln;
auto a =7;
auto h = (int b)=>a+b;
auto d1 = toDelegate!(int,int)(h);
void* ptr = cast(void*)
(*cast(int delegate(int)*) ptr)(10).writeln;
d1(21).writeln;
h(32).writeln;
}
```
Output:
10
46
17
28
39
Which is what is expected.
Re: What am I doing wrong here?
On Friday, 6 May 2022 at 18:04:13 UTC, JG wrote:
```d
//...
struct Adder {
int a;
int opCall(int b) { return a+b; }
}
auto adder(int a) {
auto ret = Adder.init;
ret.a=a;
return ret;
}
void main() {
auto g = adder(5);
g(5).writeln; // 10
auto d = toDelegate!(int, int)(g);
d(5).writeln; // 10
// ...
}
```
The value returned by the delegate structure in the above line is
10. Its parameter is 5, but if you do it to 21, you will get 42.
So it doesn't have the ability to delegate Adder.
In summary, the sum function isn't executing. Instead, its value
gets double.
SDB@79
Re: What am I doing wrong here?
On Friday, 6 May 2022 at 18:35:40 UTC, Ali Çehreli wrote: On 5/6/22 11:04, JG wrote: > [...] This is a segmentation fault. Reduced: import std; [...] Hi, thanks. That was quite silly. (I was thinking the variable lives to the end of scope of main but not thinking about that I am passing by value).
Re: What am I doing wrong here?
On 5/6/22 11:04, JG wrote:
> This isn't code to be used for anything (just understanding).
This is a segmentation fault. Reduced:
import std;
struct Delegate(A,B) {
B function(void* ptr, A a) f;
void* data;
B opCall(A a) {
return f(data,a);
}
}
auto toDelegate(A, B,S)(S s) {
static B f(void* ptr, A a) {
return (*(cast(S*) ptr))(a);
}
Delegate!(A,B) ret;
ret.f=
ret.data= cast(void*)
return ret;
}
void main() {
auto a =7;
auto h = (int b)=>a+b;
auto d1 = toDelegate!(int,int)(h);
d1(10);
}
This is what I did to figure out:
1) Compiled with -g
2) Started gdb (my compiled program is 'deneme'):
$ gdb --args ./deneme
3) Entered 'run' in gdb
You are storing the address of the local variable 's' here:
ret.data= cast(void*)
One good news is, compiling with -dip1000 catches this mistake. :)
Another solution is to pass 's' by ref, in which case you have to make
sure that variable lives long enough when its used.
// vvv
auto toDelegate(A, B,S)(ref S s) {
// ...
}
Further, you can mix -dip1000 and ref if you protect the code by also
adding 'return' to the parameter:
// vv
auto toDelegate(A, B,S)(return ref S s) {
// ...
}
I am surprised that 'in' does not provide similar protection.
// vv
auto toDelegate(A, B,S)(in S s) {
The code compiles but crashes. (?)
Ali
What am I doing wrong here?
This isn't code to be used for anything (just understanding).
```d
import std;
struct Delegate(A,B) {
B function(void* ptr, A a) f;
void* data;
B opCall(A a) {
return f(data,a);
}
}
auto toDelegate(A, B,S)(S s) {
static B f(void* ptr, A a) {
return (*(cast(S*) ptr))(a);
}
Delegate!(A,B) ret;
ret.f=
ret.data= cast(void*)
return ret;
}
struct Adder {
int a;
int opCall(int b) { return a+b; }
}
auto adder(int a) {
auto ret = Adder.init;
ret.a=a;
return ret;
}
void main() {
auto g = adder(5);
g(5).writeln;
auto d = toDelegate!(int, int)(g);
d(5).writeln;
auto a =7;
auto h = (int b)=>a+b;
auto d1 = toDelegate!(int,int)(h);
void* ptr = cast(void*)
(*cast(int delegate(int)*) ptr)(10).writeln;
d1(10).writeln;
h(10).writeln;
}
```
What am I doing wrong here?
Hey everyone, I'm new to D so bare with me please. I've been
trying to figure out what's up with the strange forward refernce
errors the compiler (DMD 2.060) is giving me. Here's a code
snippet that's generating a forward reference error:
public class AliasTestClass(alias func)
{
static assert(__traits(isStaticFunction, func));
}
public class TestClass
{
private AliasTestClass!(randomFunction) test; // -
public static void randomFunction()
{
}
}
The strange part about it is that if I surround the
randomFunction parameter with another pair of paranthesis like so
private AliasTestClass!((randomFunction)) test;
It works just fine. If I don't, however, I get a forward
reference error:
Error: template instance main.AliasTestClass!(randomFunction)
forward reference of randomFunction
Am I doing anything wrong or is this some kind of bug?
Re: What am I doing wrong here?
On 2012-10-14, 14:28, Martin wrote:
Hey everyone, I'm new to D so bare with me please. I've been trying to
figure out what's up with the strange forward refernce errors the
compiler (DMD 2.060) is giving me. Here's a code snippet that's
generating a forward reference error:
public class AliasTestClass(alias func)
{
static assert(__traits(isStaticFunction, func));
}
public class TestClass
{
private AliasTestClass!(randomFunction) test; // -
public static void randomFunction()
{
}
}
The strange part about it is that if I surround the randomFunction
parameter with another pair of paranthesis like so
private AliasTestClass!((randomFunction)) test;
It works just fine. If I don't, however, I get a forward reference error:
Error: template instance main.AliasTestClass!(randomFunction) forward
reference of randomFunction
Am I doing anything wrong or is this some kind of bug?
It's a bug. Maybe it's already in Bugzilla (there are some forward-ref
bugs there already). Please file:
http://d.puremagic.com/issues/enter_bug.cgi
--
Simen
Re: What am I doing wrong here?
On Sunday, 14 October 2012 at 12:58:24 UTC, Simen Kjaeraas wrote:
On 2012-10-14, 14:28, Martin wrote:
Hey everyone, I'm new to D so bare with me please. I've been
trying to figure out what's up with the strange forward
refernce errors the compiler (DMD 2.060) is giving me. Here's
a code snippet that's generating a forward reference error:
public class AliasTestClass(alias func)
{
static assert(__traits(isStaticFunction, func));
}
public class TestClass
{
private AliasTestClass!(randomFunction) test; // -
public static void randomFunction()
{
}
}
The strange part about it is that if I surround the
randomFunction parameter with another pair of paranthesis like
so
private AliasTestClass!((randomFunction)) test;
It works just fine. If I don't, however, I get a forward
reference error:
Error: template instance main.AliasTestClass!(randomFunction)
forward reference of randomFunction
Am I doing anything wrong or is this some kind of bug?
It's a bug. Maybe it's already in Bugzilla (there are some
forward-ref
bugs there already). Please file:
http://d.puremagic.com/issues/enter_bug.cgi
Oh, thank you for clarifying, I thought I was doing something
wrong :)
