Getting back into clojure recently has made me realize how nice lisp is in that is has almost no "syntax". Everything on a page of clojure code is basically just function calls; so really there's just two kinds of things: function names and arguments. Syntax highlighting for lisp as such I think should reflect that simplicity.

So I decided I'd write my own (minimal) syntax highlighter for my preferred editor vis in LPEG. What I wanted in my syntax highlighter for lisp to highlight was simple: (1) comments, (2) function names (e.g. the first parameter in lists), and (3) the first function argument (e.g. all function second argument in case of defn etc.)

Here's the final lpeg highlighter code (e.g. add to ~/.config/vis/themes/mlisp.clj and then set syntax=mlisp):

local l = require('lexer')
local token, word_match = l.token, l.word_match
local P, R, S, C = lpeg.P, lpeg.R, lpeg.S, lpeg.C
local M = {_NAME = 'lisp'}

local line_comment = ';' * l.nonnewline^0
local block_comment = '#_(' * (l.any - ')')^0 * P(')')
local firstargchars = l.any - ' ' - ')' - '(';
local secondargchars = l.any - ' ' - ')' - '(' - '[' - ']' - '"';

local fn_call_arg_one = token(
  l.KEYWORD, lpeg.B('(') * (firstargchars)^1
);
local fn_call_arg_two  = token(
  l.TYPE, (' ' * secondargchars^1)^-1
);
local comment = token(
  l.COMMENT, line_comment + block_comment
);

M._rules = {
  {'fn_call', fn_call_arg_one * fn_call_arg_two },
  {'comment', comment}
};

return M;