How to pass multiple arguments to hc-highlight-chars?

Question

How do you pass arguments to a function using lambda? I have looked through:
https://www.gnu.org/software/emacs/manual/html_node/elisp/Argument-List.html#Argument-List
and
https://www.emacswiki.org/emacs/download/highlight-chars.el
The only examples I found in the 2nd link were for tabs and whitespaces which use functions requiring no arguments.

Here's what I have tried so far:
1.

  (require 'highlight-chars)
  (defun my:add-semi-colon-highlighting ()
    (add-hook 'font-lock-mode-hook
              (lambda () (hc-highlight-chars ";" "highlight"))))

  (add-hook 'c-mode-common-hook 'my:add-semi-colon-highlighting)

2.

  (require 'highlight-chars)
  (defun my:add-semi-colon-highlighting ()
    (add-hook 'font-lock-mode-hook
              (lambda () (hc-highlight-chars (";","highlight")))))

  (add-hook 'c-mode-common-hook 'my:add-semi-colon-highlighting)

3.

  (require 'highlight-chars)
  (defun my:add-semi-colon-highlighting ()
    (add-hook 'font-lock-mode-hook
              (lambda () (hc-highlight-chars ";" highlight))))

  (add-hook 'c-mode-common-hook 'my:add-semi-colon-highlighting)

Not sure if this should go into another question or not, but if wanted to customize the face for ";" (E.g red foreground and current background), how would I do that in the my:add-semi-colon-highlighting function?

Answer 1

#2 is not Lisp - no comma.

#1 and #3 are almost right. And admittedly the doc for this function is a bit complex on this matter.

So the answer to your general question about passing multiple arguments is to do as you did (except for #2, with the comma).

The answer to your specific question about hc-highlight-chars is to use this code: (hc-highlight-chars '(";") 'highlight).

Interactively, as the doc says, you enter first the characters and then the name of a face. And a name is indeed a string, such as "highlight".

But at the end of the doc string you see a description of the arguments for non-interactive use, and there it says that argument FACE is a face. I've now clarified that further by adding (e.g., a symbol) after it. A face is typically a symbol.

For argument CHARS things are more complex. For that the doc says:

CHARS is a possible value for `hc-other-chars', that is, a list of
entries such as described above.

And you really need to consult the doc above, which explains that the spec of which chars to highlight is a list, each of whose elements can take multiple forms, one of which is a string of characters. (";") is a list of one element that is a string of characters.

If you look more into the code you'll see that hc-highlight-chars already uses add-hook to add to font-lock-mode-hook. It does this, for the current case:

(add-hook 'font-lock-mode-hook
          (lambda () (hc-highlight-other-chars '("ab") nil 'highlight))  
          'APPEND)

It can help perhaps to start by using hc-highlight-chars interactively, to get the hang of what it does.

The doc (the file Commentary and other doc strings) tells you more about hc-highlight-other-chars, other workhorse functions, and user option hc-other-chars. You might need to read it twice to understand it all well, but I think the necessary info is there. Let me know if you find that's not the case.

As for your question about customizing a face: Do you mean how to customize face highlight, which you used in your example? If so, the answer is M-x customize-face highlight.

Or did you mean create a new face to use, which has attributes that you choose? For that, you use defface -- see the Elisp manual, node Defining Faces.

Or did you perhaps mean provide a face specification on the fly, without changing any existing defined face or defining a new one (defface)? You can do that this way, for example:

`(hc-highlight-chars '(";") '(:foreground "red" :background "green"))`

(This is why the doc describing the FACE parameter to the function says that it is a face, without saying that it must be a symbol. A face can also be just such a property list (plist) of face attributes and their values.)