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One can use Jacinda to generate tags files for vim. This amounts to string processing with regular expressions, which we can do in a functional style, skirting Universal Ctags.

According to :help tags-file-format, the format for a tags file is:

{tagname}       {TAB} {tagfile} {TAB} {tagaddress}

In vim, a {tagaddress} can be any ex command, and in fact using regular expressions will ensure our tag files do not become outdated as quickly. For instance:

sum prelude/fn.jac  /^fn sum(x) :=$/;

Here is our code:

fn mkEx(s) :=
  '/^' + s + '$/;';
fn processStr(s) :=
  let
    val line := split s /[ \(]+/
    val outLine := sprintf '%s\t%s\t%s' (line.2 . fp . mkEx s)
  in outLine end;
processStr"{%/fn +[[:lower:]][[:latin:]]*.*:=/}{`0}

This uses implicit syntax for streams, plus some familiar functional programming. /fn +[[:lower:]][[:latin:]]\*.\*:=/ matches only those lines where a function is defined and /[ \\(]+/ splits away the fn to get the function name.

Note also the atypical (as yet undocumented) syntax for tuples; . is the separator rather than ,.

One can run this on all .jac files in a directory with:

fd '.jac$' -x ja run tags.jac -i > tags

This gives:

sum ./prelude/fn.jac    /^fn sum(x) :=$/;
drop    ./prelude/fn.jac    /^fn drop(n, str) :=$/;
take    ./prelude/fn.jac    /^fn take(n, str) :=$/;
round   ./prelude/fn.jac    /^fn round(x) := |. (x+0.5);$/;
itostring   ./prelude/fn.jac    /^fn itostring() :=$/;
any ./prelude/fn.jac    /^fn any(p, xs) :=$/;
all ./prelude/fn.jac    /^fn all(p, xs) :=$/;
id  ./prelude/fn.jac    /^fn id(x) := x;$/;
fromMaybe   ./prelude/fn.jac    /^fn fromMaybe(a, x) :=$/;
replace ./prelude/fn.jac    /^fn replace(re, t, str) :=$/;
path    ./examples/path.jac /^fn path(x) :=$/;
printSpan   ./examples/span.jac /^fn printSpan(str) :=$/;
mkEx    ./examples/tags.jac /^fn mkEx(s) :=$/;
processStr  ./examples/tags.jac /^fn processStr(s) :=$/;
...

I think this would be more useful in awk, since that is more universal than ctags, however, the example is a testament to Jacinda's utility.