http://d.puremagic.com/issues/show_bug.cgi?id=4464
Summary: std.range.take does not always return Take!R Product: D Version: D2 Platform: All OS/Version: All Status: NEW Severity: normal Priority: P2 Component: Phobos AssignedTo: nob...@puremagic.com ReportedBy: yebbl...@gmail.com --- Comment #0 from yebblies <yebbl...@gmail.com> 2010-07-15 05:46:13 PDT --- When used with a range that supports slicing, take(r, n) returns r[0..n], which unfortunately makes it impossible to declare a variable of type Take!R and have it work in all situations. I do consider this a bug and not an intended part of the design, please correct me if this is not the case. eg. int[] a; Take!R r = take(a, 3); // type mismatch error In most situations this is not a problem as type inference can be used, but when the type need to be known (as in a struct declaration) it won't work. Because take is an auto function, typeof(take(r, n)) does not work either. To fix this without disabling the slicing optimisation: 1. Change the template constraint on 'Take' - struct Take(R) if (isInputRange!(R)) + struct Take(R) if (isInputRange!(R) && !hasSlicing!R) 2. Add a template to handle the other case + template Take(R) if (isInputRange!R && hasSlicing!R) + { + alias typeof(R.init[0..R.init.length]) Take; + }; 3. Change the return type of take from 'auto' to 'Take!R' - auto take(R)(R input, size_t n) if (isInputRange!R && hasSlicing!R) + Take!R take(R)(R input, size_t n) if (isInputRange!R && hasSlicing!R) With these changes take and Take work properly with everything. I _will_ learn how to make real diffs one day. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------