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[Andrei Alexandrescu]

Benji Smith wrote:
> Andrei Alexandrescu wrote:
>> Daniel Keep wrote:
>>>
>>> Andrei Alexandrescu wrote:
>>>> Michel Fortin wrote:
>>>>> On 2009-08-09 11:10:48 -0400, Andrei Alexandrescu
>>>>> <SeeWebsiteForEmail at erdani.org> said:
>>>>>
>>>>>>> It's also arguable that all functions in std.string should take
>>>>>>> const(char)[]. Or, you know, const(T)[], since D supports encodings
>>>>>>> other than UTF-8, despite what std.string leads you to believe.
>>>>>> Yah, I think they should all be parameterized so they can work with
>>>>>> various character widths and even encodings.
>>>>> But shouldn't they work with *ranges* in general, a string being only
>>>>> a specific case?
>>>> That's true as well! In my dreams, me and the famous actress... oh 
>>>> wait,
>>>> wrong dream. In my dreams, I eliminate std.string and put all of its
>>>> algorithms, properly generalized, in std.algorithm, to work on more 
>>>> than
>>>> just arrays, and more than just characters.
>>>>
>>>> Andrei
>>>
>>> How do you define 'tolower' on non-characters?
>>
>> That and others would remain specific for characters. I do help to be 
>> able to abstract functions such as e.g. strip().
>>
>> Andrei
> 
> How would you generalize the string functions into ordinary array 
> functions while still taking into account the different character types?
> 
> For example...
> 
>    dchar needle = 'f';
>    char[] haystack = "abcdefg";
>    auto index = haystack.indexOf(needle);
> 
> That code is roughly equivalent to this code for generalized arrays, 
> which seems reasonable enough...
> 
>    float needle = 2.0;
>    double[] haystack = [ 1.0, 2.0, 3.0 ];
>    auto index = haystack.indexOf(needle);
> 
> ...since "float" is implicitly castable to "double".
> 
> But the string example has weird monkey-business going on under the 
> covers, since dchar is wider than char, and therefore a single dchar 
> element might consume multiple slots within the char[] array.
> 
> Are there any analogous examples of that behavior with other types, 
> where you'd search for a single element striding multiple indexes within 
> an array of narrower values?
> 
> --benji

Great question. I plan to add a range ByCharacter and a function 
byCharacter that spans a string one dchar at a time. Actually I have the 
implementation already, haven't checked it in yet. That's a 
bidirectional range. In that approach, if you write:

char[] haystack = "abcdefg";
auto pos = find(haystack, needle);

the search is done with the usual array semantics, but if you say:

char[] haystack = "abcdefg";
auto pos = find(byCharacter(haystack), needle);

then a dchar-at-a-time search is performed.

This idea is raw, so improvements are welcome.


Andrei