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Make Sex templates more pleasant syntactically

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No more unquotes to instantiate templates.
Also no need to pass quoted substitution lists, just use them as
regular lisp macros.
This commit is contained in:
alex-eg
2025-07-11 18:27:50 +03:00
parent 162d4f5322
commit 37a252f2b1
5 changed files with 118 additions and 72 deletions
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58
Readme.org
View File

@@ -90,32 +90,31 @@ struct foo {
};
#+end_src
** Templating (and Chickening)
** Syntactic templates
Sex has support for template substitutions. Any piece of code can be
templated. After declaring, templates should be instanced in order to
be used. To instance template, use ~,~-prefixed form in Sex
code. During instancing, template arguments in the body get
replaced with provided values by the following rules:
templated. Template declarations look like functions: they have a
name, an argument list and a body. When declared template is
encountered during reading of Sex code, its body will udergo syntactic
rewriting using the provided values by the following rules:
1. If the value is a symbol, all arguments in a body are replaced with
the value, and also all /parts/ of any other symbol equal to the
value also get replaced.
2. If the value is a non-symbolic form, all arguments in a body are
replaced with it, but no symbolic substitution is performed.
In general, the form of a template declaration is like this:
Formally, template declaration has the following syntax:
#+begin_src
(template (name (substitute-args ...) other-args ...)
body ...)
(template (name . substitute-args) . body)
#+end_src
*** Examples:
**** Structure with templated value type
#+begin_src
(template (foo (T))
(struct foo-T
((T value))))
(template (foo ?T)
(struct foo-?T
((?T value))))
,(foo '(float))
(foo float)
#+end_src
->
#+begin_src
@@ -126,17 +125,20 @@ struct foo_float {
};
#+end_src
Note that ~?~ at the start of template argument is not syntax, just
convention.
**** Wrapper for checking return codes
#+begin_src
(template (check-sdl-return (call message ret-code))
(template (check-sdl-return call message ret-code)
(if (< 0 call)
(begin
(puts message)
(return ret-code))))
(fn int init ()
,(check-sdl-return
'((SDL-Init SDL-INIT-VIDEO) "Failed to initialize SDL" 1))
(check-sdl-return
(SDL-Init SDL-INIT-VIDEO) "Failed to initialize SDL" 1)
...)
#+end_src
->
@@ -152,23 +154,23 @@ static int init () {
**** A bit of everything
#+begin_src
(template (list-T (T))
(struct list-T
((T value)
((* list-T) next))))
(template (list-T ?T)
(struct list-?T
((?T value)
((* list-?T) next))))
(template (list-for-each (what-do type list-var elt-var))
(template (list-for-each type list-var elt-var body)
(var type elt-var (-> list-var value))
(while (!= (-> list-var next) NULL)
what-do
body
(= list-var (-> list-var next))
(= elt-var (-> list-var value))))
; ... somewhere later
,(list-T '(int))
(list-T int)
(pub fn void print-list (const list-int *l)
,(list-for-each '((printf "%d " v) int l v))
(pub fn void print-list (((const list-int) *l))
(list-for-each int l v (printf "%d " v))
(printf "\n"))
#+end_src
Then will be expanded in the following code:
@@ -177,7 +179,7 @@ Then will be expanded in the following code:
(struct list_int ((int value) ((* list_int) next)))
(%fun void
print_list
(const list_int *l)
(((const list_int) *l))
(%var int v (-> l value))
(while (!= (-> l next) NULL)
(printf "%d " v)
@@ -195,7 +197,7 @@ struct list_int {
list_int *next;
};
void print_list (int const, int list_int, int *l) {
void print_list (const list_int *l) {
int v = l->value;
while (l->next != NULL) {
printf("%d ", v);
@@ -206,10 +208,6 @@ void print_list (int const, int list_int, int *l) {
}
#+end_src
Also, as a bonus, not only a template can be used after ~,~ in Sex
source, but in fact any Chicken code you want to run during the
transpilation.
** Use an established environment for development
As Sex is S-expressions, you always have Emacs with paredit as your
best option.

30
example/list.seh
View File

@@ -1,34 +1,34 @@
(template (list-T (T))
(struct list-T
((T value)
((* list-T) next))))
(template (list-T ?T)
(struct list-?T
((?T value)
((* list-?T) next))))
(template (make-list-T (T) is-public?)
(,@(if is-public? '(pub) '()) fn (* list-T) make-list-T ()
(var (* list-T) list (cast (* list-T) (malloc (sizeof list-T))))
(template (make-list-T ?T is-public?)
(,@(if 'is-public? '(pub) '()) fn (* list-?T) make-list-?T ()
(var (* list-?T) list (cast (* list-?T) (malloc (sizeof list-?T))))
(= (-> list next) NULL)
list))
(template (add-value-list-T (T) is-public?)
(,@(if is-public? '(pub) '()) fn void add-value-list-T ((list-T *list) (T value))
(template (add-value-list-?T ?T is-public?)
(,@(if 'is-public? '(pub) '()) fn void add-value-list-?T ((list-?T *list) (T value))
(while (!= (-> list next) NULL)
(= list (-> list next)))
(= (-> list next) (make-list-T))
(= (-> list next) (make-list-?T))
(= (-> list value) value)))
(template (length-list-T (T) is-public?)
(,@(if is-public? '(pub) '()) fn size-t length-list-T ((list-T *list))
(template (length-list-?T ?T is-public?)
(,@(if 'is-public? '(pub) '()) fn size-t length-list-?T ((list-?T *list))
(var size-t n 0)
(while (!= (-> list next) NULL)
(= list (-> list next))
(++ n))
n))
(template (is-empty-list-T (T) is-public?)
(,@(if is-public? '(pub) '()) fn bool is-empty-list-T ((list-T *list))
(template (is-empty-list-?T ?T is-public?)
(,@(if 'is-public? '(pub) '()) fn bool is-empty-list-?T ((list-?T *list))
(== (-> list next) NULL)))
(template (list-for-each (what-do list-var elt-var))
(template (list-for-each list-var elt-var what-do)
(var int elt-var (-> list-var value))
(while (!= (-> list-var next) NULL)
what-do

32
example/test-list.sex
View File

@@ -18,11 +18,11 @@
(var foo f #((= .a-field 1.2)))
,(list-T '(int))
,(make-list-T '(int) #f)
,(add-value-list-T '(int) #f)
,(length-list-T '(int) #f)
,(is-empty-list-T '(int) #f)
(list-T int)
(make-list-T int)
(add-value-list-T int)
(length-list-T int)
(is-empty-list-T int)
(extern fn void puk ((int a) (float b)))
(fn int bar () ,(imports-test 10 20 30))
@@ -38,7 +38,8 @@
(add-value-list-int l 3)
(add-value-list-int l 4)
(printf "Size of the list: %zu\n" (length-list-int l))
,(list-for-each '((printf "%d " v) l v))
(list-for-each l v
(printf "%d " v))
(printf "\n")
(printf "%zu\n" l->next)
0)
@@ -47,3 +48,22 @@
(pub fn void clear-command-buffer ((segs-renderer *r)))
(pub fn void add-render-command ((segs-renderer *r) ((fn void ()) command)))
(pub fn void commit-command-buffer ((segs-renderer *r)))
(template (list-T ?T)
(struct list-?T
((?T value)
((* list-?T) next))))
(template (list-for-each type list-var elt-var body)
(var type elt-var (-> list-var value))
(while (!= (-> list-var next) NULL)
body
(= list-var (-> list-var next))
(= elt-var (-> list-var value))))
; ... somewhere later
(list-T int)
(pub fn void print-list (((const list-int) *l))
(list-for-each int l v (printf "%d " v))
(printf "\n"))

21
sexc.scm
View File

@@ -3,6 +3,7 @@
(import brev-separate
(chicken pathname)
(chicken plist)
(chicken pretty-print)
(chicken process-context)
(chicken string)
@@ -83,6 +84,14 @@
(char=? #\. (string-ref (symbol->string (car form)) 0)))
(cons (make-field-access form) acc))
;; another special case - template
((template? form)
(append (fold
walk-generic
(list)
(eval form))
acc))
;; toplevel, or a start of a regular list form
(else
(let ((new-acc (list)))
@@ -134,8 +143,17 @@
(append (walk-generic (list 'static (cdr form)) (list)) acc))
(else (error "Pub what?"))))
(define (template? form)
(and (list? form)
(symbol? (car form))
(get (car form) 'sex-template)))
(define (walk-sex-tree form acc)
(if (list? form)
(if (template? form)
(fold (fn (walk-sex-tree x y))
acc
(eval form))
(case (car form)
((fn) (walk-function form #t acc))
((extern) (walk-extern form acc))
@@ -144,8 +162,7 @@
((unquote) (fold (fn (walk-sex-tree x y))
acc
(eval (cadr form))))
(else (append (walk-generic form (list)) acc)))
(else (append (walk-generic form (list)) acc))))
;; only for unquote support
(list (list (atom-to-fmt-c form)))))

25
templates.scm
View File

@@ -1,18 +1,27 @@
(declare (unit templates))
(import brev-separate
(import
(chicken plist)
brev-separate
fmt
regex
srfi-1 ; list routines
tree)
(define (register-template name)
(put! name 'sex-template #t))
(define-syntax template
(syntax-rules ()
((_ (name subst-list args ...) body ...)
(define (name subst-list-arg args ...)
(let* ((subst-alist (map cons 'subst-list subst-list-arg))
(replaced-body (apply-substitution `(body ...) subst-alist)))
replaced-body)))))
((template (name . args) . body)
(begin
(register-template 'name)
(define-syntax name
(syntax-rules ()
((name . applied-args)
(let* ((subst-alist (map cons 'args 'applied-args))
(replaced-body (apply-substitution `body subst-alist)))
replaced-body))))))))
(define (apply-symbol-substitution sym subst-alist)
;; All non-symbol substitutions will be filtered.
@@ -22,7 +31,9 @@
(subst-map (map (fn
(if (symbol? (car x))
(cons
(fmt #f "([^\\-]?)" (symbol->string (car x)) "([\\-$]?)")
(fmt #f "([^\\-]?)"
(regexp-escape (symbol->string (car x)))
"([\\-$]?)")
(fmt #f "\\1" (symbol->string (cdr x)) "\\2"))
x))
(filter (fn (symbol? (cdr x))) subst-alist))))