Re: vim diff

" File: diffbyline.vim
" Created: 2010 Sep 28
" Last Change: 2010 Oct 02
" Rev Days: 3
" Author: Andy Wokula <anwoku@yahoo.de>

" :SetLineByLineDiff[!]
"
" set the 'diffexpr' to enable a trivial line-by-line diff algorithm (the
" diff program has no option for this). Reset 'diffexpr' with [!].

com! -bar -bang SetLineByLineDiff call s:SetDiffExpr(<bang>0)

func! s:SetDiffExpr(bang)
if !a:bang
set diffexpr=DiffLineByLine()
echo "'diffexpr' changed to enable line-by-line diff"
else
" XXX restore the previous value
set diffexpr&
echo "'diffexpr' restored"
endif
endfunc

func! DiffLineByLine()
let result = [] " diff output lines
let oldlines = readfile(v:fname_in)
let newlines = readfile(v:fname_new)

let len_oldlines = len(oldlines)
let len_newlines = len(newlines)
let len_common = min([len_oldlines, len_newlines])

" different number of lines allowed
" first common lines -> change(s) only
" rest -> append (er, no, see below)

let idx = 0
let change_start = -1
while idx < len_common
if oldlines[idx] !=# newlines[idx]
" XXX above test is case sensitive and ignores 'diffopt'
if change_start == -1
let change_start = idx
endif
let change_end = idx
elseif change_start >= 0
" line-idx is just after a block of changed lines

" prepare a diff block
if change_start < change_end
let range = (1+change_start). ",". (1+change_end)
else
let range = 1+change_start
endif
let ed_cmd = range. "c". range
call add(result, ed_cmd)
call extend(result, map(oldlines[change_start : change_end], '"< ". v:val'))
call add(result, '---')
call extend(result, map(newlines[change_start : change_end], '"> ". v:val'))

let change_start = -1
endif
let idx += 1
endwhile

if change_start >= 0

" XXX extract to function? (paragraph copied from above)
if change_start < change_end
let range = (1+change_start). ",". (1+change_end)
else
let range = 1+change_start
endif
let ed_cmd = range. "c". range
call add(result, ed_cmd)
call extend(result, map(oldlines[change_start : change_end], '"< ". v:val'))
call add(result, '---')
call extend(result, map(newlines[change_start : change_end], '"> ". v:val'))

endif

if len_oldlines < len_newlines
let append_start = len_oldlines
let append_end = len_newlines - 1
let old_range = append_start " append below this line
if append_start < append_end
let new_range = (1+append_start). ",". (1+append_end)
else
let new_range = 1+append_start
endif
let ed_cmd = old_range. "a". new_range
call add(result, ed_cmd)
call extend(result, map(newlines[append_start : append_end], '"> ". v:val'))

elseif len_oldlines > len_newlines
let delete_start = len_newlines
let delete_end = len_oldlines - 1
let new_range = delete_start " delete below this line
if delete_start < delete_end
let old_range = (1+delete_start). ",". (1+delete_end)
else
let old_range = 1+delete_start
endif
let ed_cmd = old_range. "d". new_range
call add(result, ed_cmd)
call extend(result, map(oldlines[delete_start : delete_end], '"< ". v:val'))

endif

" Decho result
" XXX strange: :Decho prints at least two result lists, first is
" ['1c1', '< line1', '---', '> line2'] and belongs nowhere (is this an
" internal diff test by Vim?)

call writefile(result, v:fname_out)

endfunc
Am 24.08.2010 04:31, schrieb rudy b:
> Hi,
> I have a question about "diff".
> I've always found "diff" very powerful, and I've never had any issue
> with this commad.
> Expect that I encoutered a problem, that I wish "diff" would be just
> slightly more flexible.
>
> Usually "diff" is very smart in aligning the lines in a way to
> optimise its match.
> Is there any way that I can set some sort of flag for the "diff"
> command to start comparing the files line by line ONLY (and not try to
> use any of its smart matching algorithms) ?
> line#1 (file1) .... line#1 (file2)
> line#2 (file1) .... line#2 (file2)
> line#3 (file1) .... line#3 (file2)
> ...
> line#n (file1) .... line#n (file2)
>
> thanks in advance,
> Rudy

This kind of diff can be done in Vimscript, see attached plugin! It's
simple yet, for example 'diffopt' is ignored.

Usage:

:SetLineByLineDiff
enable line-by-line diff (set 'diffexpr' to a different value)

:SetLineByLineDiff!
disable, set 'diffexpr' back to the default

--
Andy

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