Re: [PATCH] add 'string-distance' to calculate Levenshtein distance

[chen bin]

Hi, Eli,

Attached is latest patch. It will use byte compare aglorithm if both
strings are not multi-byte strings.

Regards,
Chen

On Fri, Apr 20, 2018 at 12:55 AM, chen bin <address@hidden> wrote:
> Hi, Eli,
> I attached the new patch.
>
> A software project usually contains nomal directory and file names.
> Linux kernel source, for example.
>
> My package `counsel-etags` will use byte compare version.
>
> Regards,
> Chen
>
> On Thu, Apr 19, 2018 at 6:05 PM, Eli Zaretskii <address@hidden> wrote:
>>> From: chen bin <address@hidden>
>>> Date: Tue, 17 Apr 2018 22:31:20 +1000
>>> Cc: address@hidden
>>>
>>> As you suggested, I re-write the code using 'FETCH_STRING_CHAR_ADVANCE'.
>>
>> Thanks.
>>
>>> I also implemented the byte comparing version. It's 4 times as fast. And I 
>>> do
>>> need use it to compare file path in my package 'counsel-etags'.
>>
>> File names are just strings for this purpose, and they can potentially
>> include any non-zero characters.  So I don't see why they are special.
>>
>>> The fille path couldn't contain any funny characters (emoji). so
>>> it'sperfectly fine
>>> to use byte comparing version.
>>
>> File names can very well include emoji and other "funny" characters,
>> Emacs supports that on all modern systems (including even MS-Windows).
>>
>>> diff --git a/etc/NEWS b/etc/NEWS
>>> index 5aa92e2991..3cce2c48c7 100644
>>> --- a/etc/NEWS
>>> +++ b/etc/NEWS
>>> @@ -490,6 +490,8 @@ x-lost-selection-hooks, x-sent-selection-hooks
>>>  +++
>>>  ** New function assoc-delete-all.
>>>
>>> +** New function string-distance to calculate Levenshtein distance between 
>>> two strings.
>>
>> This long line should be filled using the fill-column setting we use
>> in NEWS.  Even better, make the header a short summary, like
>>
>>   ** New function 'string-distance'
>>
>> and then describe its functionality in a separate sentence that starts
>> immediately below that header.
>>
>>> +DEFUN ("string-distance", Fstring_distance, Sstring_distance, 2, 3, 0,
>>> +       doc: /* Return Levenshtein distance between STRING1 and STRING2.
>>> +If BYTECOMPARE is nil, we compare character of strings.
>>> +If BYTECOMPARE is t, we compare byte of strings.
>>
>> Please lose the "we" part, it's inappropriate in documentation,
>> because it describes what Emacs does.
>>
>>> +Comparing by byte is faster and non-ascii characters has weighted distance.
>>
>> I would delete this sentence, it is IMO confusing more than anything
>> else.  (And I still think the bytewise comparison is not needed.)
>>
>>> +  bool use_bytecompare = !NILP(bytecompare);
>>                                 ^^
>> Space between these 2 characters.
>>
>>> +  else
>>> +    {
>>> +      int c1, c2;
>>> +      ptrdiff_t i1, i1_byte, i2, i2_byte;
>>> +      i2 = i2_byte = 0;
>>> +      for (x = 1; x <= len2; x++)
>>
>> Please move the initialization of i2 and i2_byte into the for-loop
>> initializer (suing the comma operator).
>>
>>> +          i1 = i1_byte = 0;
>>> +          for (y = 1, lastdiag = x - 1; y <= len1; y++)
>>
>> Likewise here with i1 and i1_byte.
>>
>> Thanks.
>
>
>
> --
> help me, help you.



-- 
help me, help you.

0001-add-api-string-distance.patch
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