http://d.puremagic.com/issues/show_bug.cgi?id=5605
Summary: foreach with ranges doesn't support opSlice() Product: D Version: D2 Platform: Other OS/Version: Linux Status: NEW Severity: normal Priority: P2 Component: DMD AssignedTo: nob...@puremagic.com ReportedBy: acehr...@yahoo.com --- Comment #0 from Ali Cehreli <acehr...@yahoo.com> 2011-02-17 14:19:37 PST --- TDPL mentions a very useful feature on page 381 under "12.9.1 foreach with Iteration Primitives". (Note: I am copying all of this manually; the typos are mine): It first shows a function that includes a possible "compiler rewrite" of a foreach loop: void process(SimpleList!int lst) { for (auto __c = lst; !__c.empty; __c.popFront()) { auto value = __c.front; ... // Use value of type int } } It then says <quote> .... if the iterated object offers the slice operator with no arguments lst[], __c is initialized with lst[] instead of lst. This is in order to allow "extracting" the iteration means out of a container without requiring the container to define the three iteration primitives. </quote> I couldn't get that to work with the following code: import std.stdio; struct MyRange { int theOnlyOne; @property bool empty() const { return false; } @property ref int front() { return theOnlyOne; } void popFront() {} } struct MyCollection { MyRange opSlice() const { return MyRange(); } } void main() { auto coll = MyCollection(); foreach (i; coll) { // <-- compilation error // ... } } Error: cannot infer type for i Providing the type of i as 'int' or 'ref int' produce a different error: foreach (int i; coll) { or foreach (ref int i; coll) { produce Error: no property 'opApply' for type 'MyCollection' Please note that taking a slice explicitly works: foreach (i; coll[]) { but not the feature mentioned in TDPL. Thank you, Ali -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------