[Issue 7014] New: Better union initialization syntax

d-bugmail at puremagic.com d-bugmail at puremagic.com
Fri Nov 25 17:02:48 PST 2011


http://d.puremagic.com/issues/show_bug.cgi?id=7014

           Summary: Better union initialization syntax
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2011-11-25 17:01:51 PST ---
After using several unions for a while in D, I think the syntax to initialize
fields of unions is not handy enough. An idea from GNU-C:


import std.stdio;
union Foo { int i; double d; };
void main() {
    int x;
    double y;
    Foo u = void;
    auto u1 = cast(Foo)x;
    writeln(typeof(u1).stringof);
    auto u2 = cast(Foo)y; // Error: e2ir: cannot cast y of type double to type
Foo
    writeln(typeof(u2).stringof);
}


See:
http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast-to-Union


But I don't like that GNU-C idea, a problem with cast() is that it's not
precise enough, if there are two fields like this, what is a good way to assign
's' or 'u' using a cast()?

union Foo { int s; uint u; };

So I'd like a more explicit syntax.


A solution using named arguments seems good:

union Foo { int s; uint u; };
void bar(Foo f) {}
void main() {
    bar(Foo(u:5));
}

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------


More information about the Digitalmars-d-bugs mailing list