Hi Bram,
On Tue, May 2, 2023 at 12:54 PM Bram Moolenaar <vim-dev-git...@256bit.org>
wrote:
>
> This part of the help is confusing and probably not right:
>
> The "byte" is -1 if text is added or removed.
>
> In the "from" dict this doesn't make sense. If text is added (and
> nothing modified) then "start" and "end should be equal, the position
> where the text is inserted. If text is removed then "start" gives the
> start of the removed text and "end" the end. The text exists, thus
> there is no reason to use -1.
>
>
>
If the "endbyte" is not -1, then removing a character cannot be
distinguished
from modifying a character as shown below:
Modifying the first character of a string:
:echo diff(['abc'], ['xbc'])
{'from': {'startidx': 0, 'startbyte': 0, 'endidx': 0, 'endbyte': 0},
'to': {'startidx': 0, 'startbyte': 0, 'endidx': 0, 'endbyte': 0},
'added': 0, 'modified': 1}
Adding a first character to a string:
:echo diff(['bc'], ['abc'])
{'from': {'startidx': 0, 'startbyte': 0, 'endidx': 0, 'endbyte': -1},
'to': {'startidx': 0, 'startbyte': 0, 'endidx': 0, 'endbyte': 0},
'added': 0, 'modified': 1}
In this case, if the "from.endbyte" is 0 instead of -1, then this case
cannot
be differentiated from the previous example.
Removing the first character from a string:
:echo diff(['abc'], ['bc'])
{'from': {'startidx': 0, 'startbyte': 0, 'endidx': 0, 'endbyte': 0},
'to': {'startidx': 0, 'startbyte': 0, 'endidx': 0, 'endbyte': -1},
'added': 0, 'modified': 1}
In this case, if the "to.endbyte" is 0 instead of -1, then this case cannot
be differentiated from the first example.
There are some more examples where the "endbyte" or the "startbyte" is -1:
Removing a character from the middle of a string:
:echo diff(['abc'], ['ac'])
{'from': {'startidx': 0, 'startbyte': 1, 'endidx': 0, 'endbyte': 1},
'to': {'startidx': 0, 'startbyte': 1, 'endidx': 0, 'endbyte': -1},
'added': 0, 'modified': 1}
Adding a character to the middle of a string:
:echo diff(['ac'], ['abc'])
{'from': {'startidx': 0, 'startbyte': 1, 'endidx': 0, 'endbyte': -1},
'to': {'startidx': 0, 'startbyte': 1, 'endidx': 0, 'endbyte': 1},
'added': 0, 'modified': 1}
Removing the last character from a string:
:echo diff(['abc'], ['ab'])
{'from': {'startidx': 0, 'startbyte': 2, 'endidx': 0, 'endbyte': 2},
'to': {'startidx': 0, 'startbyte': 2, 'endidx': 0, 'endbyte': -1},
'added': 0, 'modified': 1}
Adding a character to the end of a string:
:echo diff(['ab'], ['abc'])
{'from': {'startidx': 0, 'startbyte': 2, 'endidx': 0, 'endbyte': -1},
'to': {'startidx': 0, 'startbyte': 2, 'endidx': 0, 'endbyte': 2},
'added': 0, 'modified': 1}
Modifying the last character in a string:
:echo diff(['abc'], ['abx'])
{'from': {'startidx': 0, 'startbyte': 2, 'endidx': 0, 'endbyte': 2},
'to': {'startidx': 0, 'startbyte': 2, 'endidx': 0, 'endbyte': 2},
'added': 0, 'modified': 1}
Adding a new item:
:echo diff(['a'], ['a', 'b'])
{'from': {'startidx': 1, 'startbyte': -1, 'endidx': -1, 'endbyte': -1},
'to': {'startidx': 1, 'startbyte': 0, 'endidx': 1, 'endbyte': 0},
'added': 1, 'modified': 0}
Removing an item from the end:
:echo diff(['a', 'b'], ['a'])
{'from': {'startidx': 1, 'startbyte': 0, 'endidx': 1, 'endbyte': 0},
'to': {'startidx': 1, 'startbyte': -1, 'endidx': -1, 'endbyte': -1},
'added': -1, 'modified': 0}
Regards,
Yegappan
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