[Issue 3017] New: doc errors in std.range (on behalf of Steven Schveighoffer)

d-bugmail at puremagic.com d-bugmail at puremagic.com
Fri May 22 10:44:06 PDT 2009


http://d.puremagic.com/issues/show_bug.cgi?id=3017

           Summary: doc errors in std.range (on behalf of Steven
                    Schveighoffer)
           Product: D
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: ASSIGNED
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: andrei at metalanguage.com
        ReportedBy: andrei at metalanguage.com


Just getting more familiar with ranges in D2, I saw the following errors in the
docs:

isInfinite: Specifies that the range must have a static member that equals
false, but it really should say that the range must have a static member *named
empty* that equals false.

advance:  mislabel, "The pass of r into *drop* is by reference", should be
advance, not drop.

retreatN: similar issue as advance, example also has mislabel.

SListRange: popFront,front: last sentence either reference a hidden member
"input" or is a copy-paste error.

=====

Couple comments I thought of, could have made another post, but...

1. advance is O(n) if slicing is not offered.  However, an infinite range
doesn't, and shouldn't, offer slicing.  But it might be able to advance n
elements in constant time if each element is well defined without a recurrence.

You may want to implement some sort of skip function, which advance uses if
slicing isn't available, and it can be supported.

For example, an infinite range of 1 to infinity could be easily skipped n
elements.  However, you don't want to offer a slice function, because the
result might or might not be an infinite range (depending on if the second
argument to the slice is $).

A stream may need a similar function.  For example, skipping n bytes could be a
quick operation.  skip should only be defined if it can be done faster than
repeatedly calling popFront.

2. Transversal, I would think, should continue to iterate over the elements
that are left (if so desired).  That is, given two ranges such as:

[1,2,3]
[4,5,6]

I would think a useful range over this would result in:

[1,4,2,5,3,6]

-Steve

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