EMACS: How to write a syntax-coloring mode for an Algol-like language that uses keyword stropping - emacs

Question

I'm trying to set up syntax colouring for Imp, an Algol-like language that uses keyword stropping, i.e. a keyword is the '%' character followed by alphabetics up to any non-alpha, such as %begin. I found that modify-syntax-entry was sufficient to colour Imp comments, but I had to use Hi-lock to colour keywords. What I'ld like help with is: how can I load the regexps for hi-lock from my ~/.emacs file when opening any file with a .imp extension, rather than having to explicitly save the rules in every individual .imp file? Here's what I have so far:
(defconst my-imp-mode-syntax-table
(let ((table (make-syntax-table)))
(modify-syntax-entry ?' "\"" table)
(modify-syntax-entry ?\" "\"" table)
(modify-syntax-entry ?! "<" table)
(modify-syntax-entry ?\n ">" table)
(modify-syntax-entry ?{ "<" table)
(modify-syntax-entry ?} ">" table)
(modify-syntax-entry ?\( "()" table)
(modify-syntax-entry ?\) ")(" table)
table))
(define-derived-mode my-imp-mode prog-mode "Simple Imp Mode"
:syntax-table my-imp-mode-syntax-table
(font-lock-fontify-buffer))
(add-to-list 'auto-mode-alist '("\\.i\\'" . my-imp-mode))
(add-to-list 'auto-mode-alist '("\\.imp\\'" . my-imp-mode))
(global-hi-lock-mode 1)
(setq hi-lock-file-patterns-policy (lambda (pattern) t))
(defface imp-keyword
'((t (:weight bold :foreground "cyan")))
"Face for IMP keywords"
:group 'hi-lock-faces)
(defface imp-constant
'((t (:foreground "green")))
"Face for IMP numeric constants"
:group 'hi-lock-faces)
;; I would like to load these patterns on opening a .imp file:
;; (("\\%[A-Za-z]*" (0 (quote imp-keyword) prepend)))
;; (("\\<[\\-+]*[0-9]*\\.?[0-9]+\\(\\|#[\\-+]?[0-9]+\\)?\\>" (0 (quote imp-constant) prepend)))
Here is an example of an Imp file:
! Hi-lock: (("\\%[A-Za-z]*" (0 (quote imp-keyword) prepend)))
! Hi-lock: (("\\<[\\-]?[0-9]*\\.?[0-9]+\\(\\#[\\-+]?[0-9]+\\)?\\>" (0 (quote imp-constant) prepend)))
%begin
! ackerman function - this is a whole-line comment
%integer x,y,j,k
%integerfn acker {short for ackerman - this is a bracketed comment by the way} (%integer m,n)
%if m = 0 %then %result = n+1
%if n = 0 %then %result = acker(m-1,1)
%result = acker(m-1, acker(m, n-1))
%end
prompt("Ackerman, First param (1..4)?"); read(x)
prompt(" Second param (1..7)?"); read(y)
write(acker(x,y), 4); newline
%endofprogram
You can see what the expected highlighting looks like by applying the elisp from above. (The details of the colouring are just a draft until I work out how to do it. I can tweak the colours etc later)

Answer 1

The Hi-lock module was not required - it is possible to write syntax colouring for a new language using the standard syntax colouring mechanism, as follows:
(defconst imp-mode-syntax-table
(let ((table (make-syntax-table)))
;; turn off ' and " from being string delimiters
(modify-syntax-entry ?' "-" table)
(modify-syntax-entry ?\" "-" table)
table))
;; Highlight comments, %stropped keywords, and numbers:
(setq imp-highlights
'(
;; many forms of comments including after labels
(";[ ]*!" ".*" nil nil (0 font-lock-comment-face))
("^[ ]*!" ".*;" nil nil (0 font-lock-comment-face))
("^[ ]*!" ".*" nil nil (0 font-lock-comment-face))
("%c\\([ ]+[%]+\\|[%]*\\)*o\\([ ]+[%]+\\|[%]*\\)*m\\([ ]+[%]+\\|[%]*\\)*m\\([ ]+[%]+\\|[%]*\\)*e\\([ ]+[%]+\\|[%]*\\)*n\\([ ]+[%]+\\|[%]*\\)*t" ".*;" nil nil
(0 font-lock-comment-face))
("%c\\([ ]+[%]+\\|[%]*\\)*o\\([ ]+[%]+\\|[%]*\\)*m\\([ ]+[%]+\\|[%]*\\)*m\\([ ]+[%]+\\|[%]*\\)*e\\([ ]+[%]+\\|[%]*\\)*n\\([ ]+[%]+\\|[%]*\\)*t" "[^$]*" nil nil
(0 font-lock-comment-face))
(":[ ]*!" "[^$]*" nil nil (0 font-lock-comment-face))
("{[^}]*}" . 'font-lock-comment-face )
("{.*$" . 'font-lock-comment-face )
;; char constants, old-style strings, and old-style based constants
("[MBOXER]?'[^']*'" . 'font-lock-constant-face)
("\"[^\"]*\"" . 'font-lock-string-face )
;; Based IMP constants
("\\<[0-9][ ]*[0-9 ]*[ ]*_[ ]*[0-9A-Fa-f][0-9A-Fa-f ]*\\>" . 'font-lock-constant-face)
;; Decimal IMP constants
("\\<[0-9][0-9 ]*\\.[ ]*[0-9][0-9 ]*#[ ]*[-+]?[ ]*[0-9][0-9 ]*\\>" . 'font-lock-constant-face)
("\\<[0-9][0-9 ]*\\.[ ]*[0-9][0-9 ]*\\>" . 'font-lock-constant-face)
;; Integer IMP constants
("\\<[0-9][ ]*[0-9][0-9 ]*\\>" . 'font-lock-constant-face)
("\\<[0-9][ ]*\\>" . 'font-lock-constant-face)
;; stropped keywords
("\\%[A-Za-z][A-Za-z]*" . 'font-lock-keyword-face )
))
(define-derived-mode imp-mode prog-mode "Simple Imp Mode"
:syntax-table imp-mode-syntax-table
(setq font-lock-defaults '(imp-highlights))
(font-lock-fontify-buffer)
)
;; Apply automatically to Imp source files:
(add-to-list 'auto-mode-alist '("\\.i\\'" . imp-mode))
(add-to-list 'auto-mode-alist '("\\.imp\\'" . imp-mode))
(add-to-list 'auto-mode-alist '("\\.imp77\\'" . imp-mode))
(add-to-list 'auto-mode-alist '("\\.imp80\\'" . imp-mode))
;; enter <esc>xfun<cr> to disable imp-mode if unwanted during an edit.
Based on the info from http://xahlee.info/emacs/emacs/elisp_syntax_coloring.html