The following code compiles, but throws at runtime.
Stack trace is at end of post.
I use dmd v2.071.2-b2 on Debian 6.
import std.stdio;
import std.algorithm;
interface IA {
@property int val();
final int opCmp(IA rhs) { return val - rhs.val; }
}
class A : IA {
private int _val;
this(int i) { _val = i; }
@property int val() { return _val; }
}
void main()
{
A[] as = [ new A(3), new A(2) ];
as.sort();
foreach (a; as)
writeln(a.val);
}
=============================================================================
When I change A[] to IA[], i.e., change the first line of main() to this:
IA[] as = [ new A(3), new A(2) ];
...then everything still builds, and doesn't throw. The runtime finds the
final opCmp in IA and uses it. The sorted output is 2, then 3.
Another workaround: Change the interface into an abstract class:
abstract class IA {
abstract @property int val();
final int opCmp(IA rhs) { return val - rhs.val; }
}
Sorting an array of (class A : AI) will then never throw, no matter whether
I declare the array as A[] or as AI[].
=============================================================================
Runtime-thrown trace for the original code:
object.Exception@src/object.d(90): need opCmp for class testinterfaceopcmp.A
----------------
??:? int object.Object.opCmp(Object) [0x441fd9]
??:? bool std.functional.binaryFun!("a < b", "a", "b").binaryFun!(testinterfaceopcmp.A, testinterfaceopcmp.A).binaryFun(ref testinterfaceopcmp.A, ref testinterfaceopcmp.A) [0x440918]
??:? void std.algorithm.sorting.__T23optimisticInsertionSortS773std10functional49__T9binaryFunVAyaa5_61203c2062VAyaa1_61VAyaa1_62Z9binaryFunTAC18testinterfaceopcmp1AZ.optimisticInsertionSort(testinterfaceopcmp.A[]) [0x441540]
??:? void std.algorithm.sorting.__T13quickSortImplS773std10functional49__T9binaryFunVAyaa5_61203c2062VAyaa1_61VAyaa1_62Z9binaryFunTAC18testinterfaceopcmp1AZ.quickSortImpl(testinterfaceopcmp.A[], ulong) [0x440b73]
??:? std.range.__T11SortedRangeTAC18testinterfaceopcmp1AVAyaa5_61203c2062Z.SortedRange std.algorithm.sorting.sort!("a < b", 0, testinterfaceopcmp.A[]).sort(testinterfaceopcmp.A[]) [0x4403fc]
??:? _Dmain [0x4400ab]
??:? _D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ6runAllMFZ9__lambda1MFZv [0x443a7e]
??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate()) [0x4439c8]
??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runAll() [0x443a3a]
??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate()) [0x4439c8]
??:? _d_run_main [0x443939]
??:? main [0x441f09]
??:? __libc_start_main [0x136c8cac]
Comment #1 by robert.schadek — 2024-12-13T18:49:33Z