Syntax highlighting for SMILES files in Vim

An image in a recent blogpost showed how the default syntax highlighting (*) in Vim looks when applied to SMILES files. A splash of pink here and there to brighten things up on a dull molecule. It's definitely doing something, but what it's doing I've no idea. So I've decided up with this I will not put any more.

Here's a simple syntax highlighting style for SMILES files. It supports three different colours for comments, the SMILES itself, and titles. If anyone has the necessary regexp-fu, it might be worth looking into highlighting different bracket levels in the SMILES string.

To use, save this file into vimfiles/syntax/smi.vim, and then use "set filetype=smi" to turn on the highlighting. To automatically do this for *.smi files, create a file vimfiles/ftdetect/smi.vim containing the line "autocmd BufRead,BufNewFile *.smi set filetype=smi".

I also looked into doing folding for such files, that is, to use any comment as a header and then fold the subsequent SMILES. This is a format I use for storing matched series, for example. It works (see foldexpr), but it's too slow for a large file, which defeats the purpose.

" Vim syntax file
" Language: SMILES strings
" Maintainer: Noel O'Boyle
" Latest Revision: 16 June 2016

if exists("b:current_syntax")
  finish
endif

syn match smiTitle /\v\s+.*$/hs=s+1
syn match smiString "\v^\S*" nextgroup=smiTitle skipwhite
syn match smiComment "\v^#.*$"

let b:current_syntax = "smi"

hi def link smiComment     Comment
hi def link smiString      Identifier
hi def link smiTitle       Include

* As the Vim documentation says, apparently it's actually lexical highlighting, but everyone calls it syntax highlighting so...