digitalmars.D.bugs - [Issue 9871] New: std.typecons.AsRange/asRange
- d-bugmail puremagic.com (110/110) Apr 03 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9871
- d-bugmail puremagic.com (33/33) Apr 03 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9871
- d-bugmail puremagic.com (10/10) Apr 04 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9871
http://d.puremagic.com/issues/show_bug.cgi?id=9871 Summary: std.typecons.AsRange/asRange Product: D Version: D2 Platform: All OS/Version: All Status: NEW Severity: enhancement Priority: P2 Component: Phobos AssignedTo: nobody puremagic.com ReportedBy: bearophile_hugs eml.cc In many situations a std.typecons.Tuple has uniform types (this means all its types are the same). Such tuples are produced by cartesianProduct(), by std.range.zip(), and so on. Later I want to process such tuples in various ways, like iterating on them, using transversal() on them, and so on (in Python code this kind of processing is common because thanks to dynamic typing tuples are like lists). If you have one of such uniform tuples like tup: import std.typecons, std.typetuple; void main() { auto tup = tuple(0, 5, 11, 22); static assert(NoDuplicates!(tup.Types).length == 1); } You can convert it to a dynamic array like this: [tup[]] So now it's usable as a range: [tup[]].map!(x => x * 2).writeln; But that syntax is a little noisy, and currently it causes a heap allocation. This avoids the heap allocation but it's wrong if the tuple is not uniform: (cast(tup.Types[0]*)&tup[0])[0 .. tup.length] So I suggest to add asRange/AsRange to std.typecons: // - - - - - - - - - - - - - - - - import std.typecons, std.typetuple, std.stdio, std.algorithm, std.range; struct AsRange(T) if (isTuple!T && NoDuplicates!(T.Types).length == 1) { alias Tfield = T.Types[0]; T inputTuple; size_t idx; // This can also be of type Tfield*. static this() { // Useless? foreach (i, _; T.Types) static assert(T.tupleof[i].offsetof == Tfield.sizeof * i); } property bool empty() { return idx >= T.length; } property Tfield front() { return (cast(Tfield*)&inputTuple[0])[idx]; } void popFront() { idx++; } // This can also be a Random Access Range. } // helper function. AsRange!T asRange(T)(T tup) if (isTuple!T && NoDuplicates!(T.Types).length == 1) { return tup.AsRange!T; } void main() { // demo auto a = [0]; auto b = [5]; auto c = [11]; auto d = [22]; Tuple!(int,int,int,int) tup = zip(a, b, c, d).front; auto result = tup.asRange.map!(x => x * 2).array; assert(result == [0, 10, 22, 44]); } // - - - - - - - - - - - - - - - - In theory simpler code is enough, but because of a current DMD bug (a limit of alias this), this can't be used with UFCS: // - - - - - - - - - - - - - - - - import std.typecons, std.typetuple, std.stdio, std.algorithm, std.range; struct AsRange(T) if (isTuple!T && NoDuplicates!(T.Types).length == 1) { alias Tfield = T.Types[0]; T inputTuple; static this() { // Useless? foreach (i, _; T.Types) static assert(T.tupleof[i].offsetof == Tfield.sizeof * i); } property Tfield[] asArray() { return (cast(Tfield*)&inputTuple[0])[0 .. T.length]; } alias asArray this; } AsRange!T asRange(T)(T tup) if (isTuple!T && NoDuplicates!(T.Types).length == 1) { return tup.AsRange!T; } void main() { // demo auto a = [0]; auto b = [5]; auto c = [11]; auto d = [22]; Tuple!(int,int,int,int) tup = zip(a, b, c, d).front; // Currently this can't be used: // Error: no property 'map' for type 'int[]' // tup.asRange.map!(x => x * 2).writeln; int[] result = tup.asRange; int[] result2 = result.map!(x => x * 2).array; assert(result2 == [0, 10, 22, 44]); } // - - - - - - - - - - - - - - - - -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Apr 03 2013
http://d.puremagic.com/issues/show_bug.cgi?id=9871 bearophile_hugs eml.cc changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|std.typecons.AsRange/asRang |std.typecons.asRange |e | A simpler implementation: import std.typecons, std.typetuple, std.stdio, std.algorithm, std.range; bool validAsRange(T)() { if (!isTuple!T || NoDuplicates!(T.Types).length != 1) return false; foreach (i, _; T.Types) // Useless? if (T.tupleof[i].offsetof != T.Types[0].sizeof * i) return false; return true; } T.Types[0][] asRange(T)(ref T tup) if (validAsRange!T()) { return (cast(T.Types[0]*)&tup[0])[0 .. T.length]; } void main() { // demo auto a = [0]; auto b = [5]; auto c = [11]; auto d = [22]; Tuple!(int,int,int,int) tup = zip(a, b, c, d).front; auto result = tup.asRange.map!(x => x * 2).array; assert(result == [0, 10, 22, 44]); } -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Apr 03 2013
http://d.puremagic.com/issues/show_bug.cgi?id=9871 bearophile_hugs eml.cc changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|std.typecons.asRange |std.typecons.asArray With the latest version I think "asArray" is a better name. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Apr 04 2013