Use regex pattern as argument to function

Question

I want to be able to pass a plain regular expression like so

autocmd BufReadPost * call TextEnableCodeSnip('bash', /^hello/, /^world/, 'SpecialComment')

To a function and use it within as a regular expression without having to convert to a string and back. I want it to have the effect of:

vimfunction! TextEnableCodeSnip(filetype,start,end,textSnipHl) abort
  " ...
  execute 'syntax region textSnip'.ft.'
  \ matchgroup='.a:textSnipHl.'
  \ keepend
  \ start=/^hello/ end=/^world/
  \ contains=@'.group
endfunction

Which modifying the function like so works fine.

I was hoping that changing the line to look like:

  \ start=start end=end

and just using the variables directly as the data type they were passed as would suffice. Unfortunately, this fails with the error:

E15: Invalid expression: "/^hello/, /^world/, 'SpecialComment')"

Which leads me to believe vim doesn't support this. Does it in another way? Or do I have to use an intermediary string?

I am new to Vimscript and couldn't find anyone else trying to do the same.

Answer 1

I would suggest to use a string for that:

autocmd BufReadPost * call TextEnableCodeSnip('bash', '^hello', '^world", 'SpecialComment')

function! TextEnableCodeSnip(filetype,start,end,textSnipHl) abort
  " ...
  execute 'syntax region textSnip'.g:ft
  \ 'matchgroup='.a:textSnipHl
  \ 'keepend'
  \ 'start=/'.a:start.'/' 'end=/'.a:end.'/'
  \ 'contains=@'.g:group
endfunction

Remark: the code seems to assume a 'ft' and 'group' global variables to exist.