• "Garett Bass" <garettbass studiotekne.com> Nov 10 2005
• Carlos Santander <csantander619 gmail.com> Nov 11 2005
• Thomas Kuehne <thomas-dloop kuehne.cn> Nov 12 2005

"Garett Bass" <garettbass studiotekne.com> writes:

I get a compiler error under v.0.138 when I try to cast a template object to
its parent interface when passing it to the delegate 
argument of opApply.  The workaround forces me to store the cast to a temporary
variable, then pass the temporary to the opApply 
delegate.

------------
private import std.stdio;

interface Foo {
    void foo();
}

class GenericFoo(T) : Foo {
    T* value;
    void foo() {
        writefln("GenericFoo!(%s).foo()", (typeid(T)).toString());
    }
}

class FooArray {
    GenericFoo!(int) gf;

    this() { gf = new GenericFoo!(int); }

    int opApply(int delegate(inout Foo) dg){
        int result = 0;
        for (int i = 0; i < 5; i++) {
            gf.value = &i;
            //result = dg(gf); // Error: cast(Foo)(gf) not an lvalue
            //result = dg(cast(Foo)gf);   // Error: ditto
            //result = dg((cast(Foo)gf)); // Error: ditto
            Foo f = cast(Foo)gf; // Workaround
            result = dg(f);      // Ok
            if (result) break;
        }
        return result;
    }
}

int main(char[][] args) {
    FooArray fa = new FooArray;
    foreach (Foo f; fa) f.foo();
    return 0;
}

------------

I suspect this test case may be generalized further, but I'm not sure how to go
about simplifying it.  Any help would be 
appreciated.

Regards,
Garett 

Carlos Santander <csantander619 gmail.com> writes:

Garett Bass escribió:
 I get a compiler error under v.0.138 when I try to cast a template object to
its parent interface when passing it to the delegate 
 argument of opApply.  The workaround forces me to store the cast to a
temporary variable, then pass the temporary to the opApply 
 delegate.
 
 ------------


 ------------
 
 I suspect this test case may be generalized further, but I'm not sure how to
go about simplifying it.  Any help would be 
 appreciated.
 
 Regards,
 Garett 
 
 


Here's a reduced version:

void foo(inout int i) {}

void main()
{
         long l;
         foo(l); //6
}

With gdc 0.16, I get: "foo.d:6: cast(int)(l) is not an lvalue". There've been 
times when allowing this has beed asked, but in the end, I think it's somewhat 
understandable behavior.

-- 
Carlos Santander Bernal

Thomas Kuehne <thomas-dloop kuehne.cn> writes:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Garett Bass schrieb am 2005-11-11:
 I get a compiler error under v.0.138 when I try to cast a template object to
its parent interface when passing it to the delegate 
 argument of opApply.  The workaround forces me to store the cast to a
temporary variable, then pass the temporary to the opApply 
 delegate.

 ------------
 private import std.stdio;

 interface Foo {
     void foo();
 }

 class GenericFoo(T) : Foo {
     T* value;
     void foo() {
         writefln("GenericFoo!(%s).foo()", (typeid(T)).toString());
     }
 }

 class FooArray {
     GenericFoo!(int) gf;

     this() { gf = new GenericFoo!(int); }

     int opApply(int delegate(inout Foo) dg){
         int result = 0;
         for (int i = 0; i < 5; i++) {
             gf.value = &i;
             //result = dg(gf); // Error: cast(Foo)(gf) not an lvalue
             //result = dg(cast(Foo)gf);   // Error: ditto
             //result = dg((cast(Foo)gf)); // Error: ditto
             Foo f = cast(Foo)gf; // Workaround
             result = dg(f);      // Ok
             if (result) break;
         }
         return result;
     }
 }

 int main(char[][] args) {
     FooArray fa = new FooArray;
     foreach (Foo f; fa) f.foo();
     return 0;
 }

 ------------

 I suspect this test case may be generalized further, but I'm not sure how to
go about simplifying it.  Any help would be 
 appreciated.


Added to DStress as
http://dstress.kuehne.cn/nocompile/i/inout_01.d

Thomas


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