• via Digitalmars-d-bugs (33/33) Aug 07 2016 https://issues.dlang.org/show_bug.cgi?id=16363

via Digitalmars-d-bugs <digitalmars-d-bugs puremagic.com> writes:

https://issues.dlang.org/show_bug.cgi?id=16363

          Issue ID: 16363
           Summary: Cannot construct a random access range using
                    frontTransversal
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: phobos
          Assignee: nobody puremagic.com
          Reporter: kirsybuu gmail.com

The current implementation of FrontTransversal and Transversal both do not
attempt to implement length or opDollar when the underlying range supports it,
thus even when using assumeNotJagged the output range will not be a random
access range.

import std.range;
void main() {
    int[][] darr = [[0, 1, 2], [4, 5, 6]];
    auto fT = frontTransversal!(TransverseOptions.assumeNotJagged)(darr);
    auto l = fT.length;
    auto s = fT[0 .. $];
    static assert(isRandomAccessRange!(typeof(fT)));
}

alex.d(5): Error: no property 'length' for type 'FrontTransversal!(int[][],
cast(TransverseOptions)2)'
alex.d(6): Error: undefined identifier '__dollar'
alex.d(7): Error: static assert 
(isRandomAccessRange!(FrontTransversal!(int[][], cast(TransverseOptions)2))) is
false

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