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created August 30, 2003 · complexity intermediate · author Usman Latif · version 5.7


I frequently need to edit tables where the fields are of varying lengths. Switching between fields is a pain as the fields can contain multiple words and using the w key is impractical. Moreover adding a new row to the table is most troublesome. The new fields need to be aligned with the old entries and tabs don't work very well. Below is an example of such a table that I pulled from the Vim user's guide:

USAGE                         RESULT    DESCRIPTION
append( {lnum}, {string})     Number    append {string} below line {lnum}
argc()                        Number    number of files in the argument list
argidx()                      Number    current index in the argument list
argv( {nr})                   String    {nr} entry of the argument list

I wrote the NextField function (given below) to automatically check the fields on the line directly above and move the cursor to the beginning of the next field. The function pads the line if required. I am using 2 or more spaces as the field separator but the field separator is an argument to the function and can be changed easily.

I have mapped <S-Tab> (Shift-Tab) to invoke the function. In the case of the above table hitting <S-Tab> anywhere on the lines after the line that starts with "append" will cause the cursor to move to the next field position or just before it depending on the context. The function will not work on the line starting with "append" as there is an empty line with no fields above it. It will work on the empty line below the table titles as there are fields on the line above it. Same is the case with the empty line below the last line of the table.

The function takes the following arguments:

fieldsep: A pattern that specifies the field separator between table columns

minlensep: Minimum length of field separator. It is used to make the function move to the next field even when the cursor is positioned less than the length of a field separator from the next table column. Set this to 0 if you are not sure what this argument is for.

padstr: The string to be used for padding when the current line needs to be padded in order to reach the next table column.

offset: The offset at which you want the cursor to be positioned in the next table column. Set it to 0 if you want the cursor positioned at the start of the next table column.

To use the function, place the code below in vimrc and add the following lines after it:

map <S-Tab> :call NextField(' \{2,}',2,' ',0)<CR>
map! <S-Tab> <C-O>:call NextField(' \{2,}',2,' ',0)<CR>

Note: If the whitespace between the fields consists of anything other than spaces, the function will not work correctly without changing the field separator. Use expandtab option if you must use tabs.

Many variations of the above idea are possible. One variation would be to have a plugin that when invoked on a specific line, extracts the field information on that line and maps the tab key to move to the next field then onwards. That way there won't be any dependence on the line directly above the cursor. If you have any suggestions of your own let me know. If enough people show interest in enhancing this feature I most likely will code an enhanced version.

" function: NextField
" Args: fieldsep,minlensep,padstr,offset
"
" NextField checks the line above for field separators and moves the cursor on
" the current line to the next field. The default field separator is two or more
" spaces. NextField also needs the minimum length of the field separator,
" which is two in this case. If NextField is called on the first line or on a
" line that does not have any field separators above it the function echoes an
" error message and does nothing.
func! NextField(fieldsep,minlensep,padstr,offset)
  let curposn = col(".")
  let linenum = line(".")
  let prevline = getline(linenum-1)
  let curline = getline(linenum)
  let nextposn = matchend(prevline,a:fieldsep,curposn-a:minlensep)+1
  let padding = ""
  if nextposn > strlen(prevline) || linenum == 1 || nextposn == 0
    echo "last field or no fields on line above"
    return
  endif
  echo ""
  if nextposn > strlen(curline)
    if &modifiable == 0
      return
    endif
    let i = strlen(curline)
    while i < nextposn - 1
      let i = i + 1
      let padding = padding . a:padstr
    endwhile
    call setline(linenum,substitute(curline,"$",padding,""))
  endif
  call cursor(linenum,nextposn+a:offset)
  return
endfunc

Comments

In my settings, I had to use offset = -1 to start exactly at the next table column.

Alternatively, change line 37 of the function from:

call cursor(linenum,nextposn+a:offset)

to:

call cursor(linenum,nextposn+a:offset-1)

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