Bug 3249 – sort and setIntersection on array of struct or class

If you create an array of struct or class, sorting does not work for std.algorthm.sort The error from using sort: C:\opt\dmd\windows\bin\..\..\src\phobos\std\algorithm.d(3620): Error: static assert "Invalid predicate passed to sort: a < b" The error from using setIntersection: C:\opt\dmd\windows\bin\..\..\src\phobos\std\functional.d(191): Error: static assert "Bad binary function q{a < b}. You need to use a valid D expression using symbols a of type S and b of type S." The code used: import std.algorithm; import std.stdio; struct S { string label; int opCmp(S s2) { if(label < s2.label) return -1; if(label > s2.label) return 1; else return 0; } } void main() { auto s1 = new S[2]; auto s2 = new S[2]; s1[0].label = "fish"; s1[1].label = "bar"; s2[0].label = "foo"; s2[1].label = "fish"; // Comment out to get setInterseciton error sort(s1); foreach(str; setIntersection(s1,s2)) writeln(str); }

This is because the default comparison is passed as a string, which does not see the definition of the struct. I'll change that to a function.