add #line directive to generated C code to support source debugging

They are not equivalent, but it'll be allright in this
case. Probably. Passes tests at least.

.github/workflows/build.yaml

@@ -0,0 +1,55 @@
+name: Sex CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build-linux:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Install chicken
+      run: |
+        wget -N https://code.call-cc.org/releases/5.4.0/chicken-5.4.0.tar.gz
+        tar zxf chicken-5.4.0.tar.gz
+        sudo apt install -y make
+        make -C chicken-5.4.0 PLATFORM=linux
+        sudo make -C chicken-5.4.0 PLATFORM=linux install
+    - name: Install dependencies
+      # FIXME: [project-local deps]: use venv or something
+      # run: make deps
+      run: sudo chicken-install $(cat dependencies.txt)
+    - name: Make sure that sexc builds
+      # FIXME: sexc being built with local .eggs/ libs needs the path at runtime.
+      # Without it there will be `Error: cannot load extension: fmt`.
+      run: make sexc && ./sexc --help
+    - name: Run tests
+      # FIXME: [project-local deps]: use local deps or build with -static
+      # run: make run-tests
+      run: make sex-tests && ./sex-tests
+
+  build-macos:
+
+    runs-on: macos-15
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Install chicken
+      run: brew install chicken make
+    - name: Install dependencies
+      # FIXME: [project-local deps]: use venv or something
+      # run: make deps
+      run: chicken-install $(cat dependencies.txt)
+    - name: Make sure that sexc builds
+      # FIXME: sexc being built with local .eggs/ libs needs the path at runtime.
+      # Without it there will be `Error: cannot load extension: fmt`.
+      run: make sexc && ./sexc --help
+    - name: Run tests
+      # FIXME: [project-local deps]: use local deps or build with -static
+      # run: make run-tests
+      run: make sex-tests && ./sex-tests

Makefile

@@ -1,5 +1,5 @@
 CHICKEN_C = csc
-CSC_FLAGS = -K prefix
+CSC_FLAGS += -K prefix
 
 MODULES = sexc fmt-c fmt-c-writer semen sex-macros sex-modules sex-reader utils
 OBJ = $(MODULES:%=%.o)

Readme.org

@@ -1,4 +1,9 @@
 * The Sex language
+
+#+NAME: the Sex logo
+#+ATTR_HTML: :width 300px
+[[sex.png][file:./sex.png]]
+
 Sex is a S-expressions language. Sex is written in Chicken, which is a
 [[https://call-cc.org][R5RS Scheme]].
 Sex is statically typed, compiled general purpose language.
@@ -13,7 +18,7 @@ to export ~CHICKEN_INSTALL_REPOSITORY~ and ~CHICKEN_REPOSITORY_PATH~
 environment variables. Refer to the documentation for more info:
 https://wiki.call-cc.org/man/5/Extension%20tools#changing-the-repository-location
 
-~chicken-install fmt getopt-long brev-separate test tree srfi-1 srfi-13 srfi-69 matchable~
+~chicken-install `cat dependencies.txt`~
 
 ** Compilation
 ~make~
@@ -49,13 +54,13 @@ An example of Sex source:
 #+begin_src scheme
 (include stdio.h)
 
-(pub fn int main ((int argc) (char **argv))
+(pub fn main ((argc int) (argv  [* const char])) int
   (puts "Hello from Sex!")
-  (var (array char 512) name)
+  (var name [char 512])
   (puts "What is your name?")
-  (scanf "%s" (cast char* &name))
+  (scanf "%s" (cast (& name) (* char)))
   (printf "Hello, %s!\n" name)
-  0)
+  (return 0))
 #+end_src
 
 Compile and run:
@@ -101,16 +106,16 @@ return Sex code.
 (pub defmacro (list-T type)
   (let ((list-type (cat 'list- type)))
     `(struct ,list-type
-       ((,type value)
-        ((* ,list-type) next)))))
+       ((value ,type)
+        (next (* ,list-type))))))
 
 (list-T int)
 #+end_src
 ->
 #+begin_src scheme
 (struct list_int
- ((int value)
-  ((* list_int) next)))
+ ((value int)
+  (next (* list_int))))
 #+end_src
 
 **** Wrapper for checking return codes
@@ -119,20 +124,19 @@ return Sex code.
   `(if (< 0 ,call)
        (begin
          (puts ,message)
-         (return ,ret-code)))))
+         (return ,ret-code))))
 
-(pub fn int init ()
+(pub fn init () int
   (check-sdl-return
     (SDL-Init SDL-INIT-VIDEO) "Failed to initialize SDL" 1)
 ...)
 #+end_src
 ->
-#+begin_src c
-(%fun int init ()
+#+begin_src scheme
+(pub fn init () int
   (if (< 0 (SDL_Init SDL_INIT_VIDEO))
-    (%begin (puts "Failed to initialize SDL") (return 1)))
+    (begin (puts "Failed to initialize SDL") (return 1)))
   ...)
-}
 #+end_src
 
 ** Use an established environment for development

dependencies.txt

@@ -0,0 +1 @@
+fmt getopt-long brev-separate test tree srfi-1 srfi-13 srfi-69 matchable

example/fns.sex

@@ -1,10 +1,10 @@
 ;;; Prototypes
-(fn void puk ())
+(fn puk () void)
 
-(pub fn void plak ())
+(pub fn plak () void)
 
 ;;; Functions
-(fn int foo () (return 1))
+(fn foo () int (return 1))
 
-(pub fn void bar ((int a) (int b))
+(pub fn bar ((a int) (b int)) void
   (printf "%d\n" (+ a b)))

example/hello-world.sex

@@ -1,9 +1,9 @@
 (include stdio.h)
 
-(pub fn int main ((int argc) (char **argv))
+(pub fn main ((argc int) (argv  [* const char])) int
   (puts "Hello from Sex!")
-  (var (array char 512) name)
+  (var name [char 512])
   (puts "What is your name?")
-  (scanf "%s" (cast char* &name))
+  (scanf "%s" (cast (& name) (* char)))
   (printf "Hello, %s!\n" name)
   (return 0))

example/lambdas.sex

@@ -1,21 +1,21 @@
 (include stdio.h)
 
-(fn int sum ((int a) (int b))
+(fn sum ((a int) (b int)) int
   (return (+ a b)))
 
-(pub fn int main ()
-  (var int a 10)
-  (var int b 20)
-  (var (fn int ((int) (int))) sum-fn sum)
+(pub fn main () int
+  (var a int 10)
+  (var b int 20)
+  (var (fn ((int) (int)) int) sum-fn sum)
 
-  (var (fn int ((int) (int))) sum-lambda
+  (var (fn ((int) (int)) int) sum-lambda
 
-       (lambda int ((int a) (int b)) ()
+       (lambda ((a int) (b int)) int ()
          (return (+ a b))))
 
-  (var (fn int ((int))) sum-lambda-2
+  (var (fn ((int)) int) sum-lambda-2
 
-       (lambda int ((int a)) ()
+       (lambda ((a int)) int ()
          (return (+ a 20))))
 
   (printf "Hello from main fn!\n")
@@ -24,15 +24,28 @@
   (printf "Calling fn ptr: %d\n" (sum-fn a b))
   (printf "Calling lambda: %d\n" (sum-lambda a b))
   (printf "Calling other lambda: %d\n" (sum-lambda-2 a))
-  (printf "Calling lambda inplace: %d\n" ((lambda int ((int a) (int b)) ()
+  (printf "Calling lambda inplace: %d\n" ((lambda ((a int) (b int)) int ()
                                             (return (+ a b 100)))
                                           a b))
 
-  (var (fn int ((int))) l-1
-       (lambda int ((int a)) ()
-         (var (fn int ((int))) l-2
-              (lambda int ((int a)) ()
+  (var (fn ((int)) int) l-1
+       (lambda ((a int)) int ()
+         (var (fn ((int)) int) l-2
+              (lambda ((a int)) int ()
                 (return (+ 60 a))))
          (return (+ 600 (l-2 a)))))
   (printf "Calling nested lambdas: %d\n" (l-1 6))
+
+  ;; Not supported yet
+  ;; Closure
+  ;;  (var (fn (fn ((int)) int) ((int))) make-adder
+  ;;       (lambda (fn int ((int a))) ()
+  ;;         (return (lambda int ((int b)) (a)
+  ;;                   (return (+ a b))))))
+  ;;
+  ;;  (var (fn int ((int))) add-10
+  ;;       (make-adder 10))
+  ;;  (var (fn int ((int))) add-20
+  ;;       (make-adder 20))
+  ;;  (printf "Calling closures: %d\n" (add-10 24))
   (return 0))

example/list.sex

@@ -1,21 +1,21 @@
 (pub defmacro (list-T type)
   (let ((list-type (cat 'list- type)))
     `(struct ,list-type
-       ((,type value)
-        ((* (struct ,list-type)) next)))))
+       ((value ,type)
+        (next (* struct ,list-type))))))
 
 (pub defmacro (make-list-T type is-public?)
   (let ((list-type (list 'struct (cat 'list- type)))
         (fn-name (cat 'make-list- type)))
-    `(,@(if is-public? '(pub) '()) fn (* ,list-type) ,fn-name ()
-      (var (* ,list-type) list (cast (* ,list-type) (malloc (sizeof ,list-type))))
+    `(,@(if is-public? '(pub) '()) fn ,fn-name () (* ,list-type)
+      (var list (* ,list-type) (cast  (malloc (sizeof ,list-type)) (* ,list-type)))
       (= (-> list next) NULL)
       (return list))))
 
 (pub defmacro (add-value-list-T type is-public?)
   (let ((list-type (list 'struct (cat 'list- type)))
         (fn-name (cat 'add-value-list- type)))
-    `(,@(if is-public? '(pub) '()) fn void ,fn-name ((,list-type *list) (,type value))
+    `(,@(if is-public? '(pub) '()) fn ,fn-name ((list * ,list-type) (value ,type)) void
       (while (!= (-> list next) NULL)
         (= list (-> list next)))
       (= (-> list next) (,(cat 'make-list- type)))
@@ -24,23 +24,24 @@
 (pub defmacro (length-list-T type is-public?)
   (let ((fn-name (cat 'length-list- type))
         (list-type (list 'struct (cat 'list- type))))
-    `(,@(if is-public? '(pub) '()) fn size-t ,fn-name ((,list-type *list))
-      (var size-t n 0)
+    `(,@(if is-public? '(pub) '()) fn ,fn-name ((list ,(cons '* list-type))) size-t
+      (var n size-t 0)
       (while (!= (-> list next) NULL)
         (= list (-> list next))
         (++ n))
       (return n))))
 
 (pub defmacro (is-empty-list-T type is-public?)
-  `(,@(if is-public? '(pub) '()) fn bool ,(cat 'is-empty-list- type)
-    ((,(list 'struct (cat 'list- type)) *list))
+  `(,@(if is-public? '(pub) '()) fn ,(cat 'is-empty-list- type)
+    ((list ,(list '* 'struct (cat 'list- type))))
+    bool
     (return (== (-> list next) NULL))))
 
 (pub defmacro (list-for-each list-type list-var elt-type elt-var what-do)
   (let ((list-var-2 (cat list-var '-2)))
     `(begin
-      (var (pointer ,list-type) ,list-var-2 ,list-var)
-      (var ,elt-type ,elt-var (-> ,list-var-2 value))
+      (var ,list-var-2 (* ,list-type) ,list-var)
+      (var ,elt-var ,elt-type (-> ,list-var-2 value))
       (while (!= (-> ,list-var-2 next) NULL)
         ,what-do
         (= ,list-var-2 (-> ,list-var-2 next))

example/test-list.sex

@@ -5,12 +5,12 @@
 (import list)
 
 (struct foo
-  ((float a-field)
-   (int b)
-   ((const char *) c)
-   ((fn bool ((bool val))) not)))
+  ((a-field float)
+   (b int)
+   (c (* const char))
+   (not (fn ((val bool)) bool))))
 
-(var (struct foo) f)
+(var f (struct foo))
 
 (list-T int)
 (make-list-T int #f)
@@ -18,15 +18,16 @@
 (length-list-T int #f)
 (is-empty-list-T int #f)
 
-(extern fn void puk ((int a) (float b)))
-(pub fn bool baz () (return true))
+(extern fn puk ((a int) (b float)) void)
+(pub fn baz () bool
+  (return true))
 
-(extern var int i)
-(var int j)
-(pub var int k)
+(extern var i int)
+(var j int)
+(pub var k int)
 
-(pub fn int main ()
-     (var (struct list-int) *l (make-list-int))
+(pub fn main () int
+     (var l (* struct list-int) (make-list-int))
      (printf "Size of the list: %lu\n" (length-list-int l))
      (add-value-list-int l 3)
      (add-value-list-int l 4)
@@ -35,9 +36,9 @@
        (printf "%d " v))
      (printf "\n")
      (printf "Size of the list: %lu\n" (length-list-int l))
-     (printf "%p\n" (cast void* l->next))
+     (printf "%p\n" (cast l->next (* void)))
      (return 0))
 
-(pub fn void print-list (((const struct list-int) *l))
+(pub fn print-list ((l (* const struct list-int))) void
      (list-for-each (const struct list-int) l int v (printf "%d " v))
      (printf "\n"))

fmt-c-writer.scm

@@ -2,15 +2,19 @@
 
 (declare (unit fmt-c-writer)
          (uses fmt-c
-               semen))
+               semen
+               utils))
 
 (import (chicken string)
+        (chicken syntax)
         brev-separate
         fmt
+        matchable
         regex
         srfi-1                          ; lists
         srfi-13                         ; strings
-        )
+        srfi-39                         ; parameters
+        tree)
 
 (define (unkebabify sym)
   (case sym
@@ -27,15 +31,13 @@
   (case atom
     ((fn) '%fun)
     ((prototype) '%prototype)
-    ((var) '%var)
     ((begin) '%block-begin)
     ((define) '%define)
     ((pointer) '%pointer)
     ((array) '%array)
     ((attribute) '%attribute)
-    ((@) 'vector-ref)
+    ((¤) 'vector-ref)
     ((include) '%include)
-    ((cast) '%cast)
     ;; uh things we do for c89 compatibility
     ((bool) 'int)
     ((true) 1)
@@ -45,6 +47,12 @@
          (unkebabify atom)
          atom))))
 
+(define (maybe-unwrap-type type)
+  (if (and (list? type)
+           (= 1 (length type)))
+      (car type)
+      type))
+
 (define (make-field-access form)
   (assert
    (= 2 (length form)) "Wrong field access format")
@@ -52,77 +60,224 @@
    (string->symbol
     (fmt #f (cadr form) (car form)))))
 
-(define (walk-generic form acc)
-  (cond
-   ((null? form) (cons '() acc))
+(define (walk-generic-toplevel form)
+  (cond ((atom? form) (atom-to-fmt-c form))
+        ((list? form) (map walk-generic-toplevel form))
+        (else (error "Malformed form " form))))
 
-   ;; vector, e.g. {}-initializer
-   ((vector? form)
-    (cons
+(define (field-access-form? form)
+  (and (symbol? (car form))
+       (char=? #\. (string-ref (symbol->string (car form)) 0))))
+
+(define (walk-expr form)
+  (match form
+    ((? vector?)
      (list->vector
-      (car (walk-generic (vector->list form) (list))))
-     acc))
+      (walk-expr (vector->list form))))
+    ((? atom?)
+     (atom-to-fmt-c form))
+    ((? field-access-form?)
+     (make-field-access form))
+    (('var . _) (walk-var form))
+    (('cast expr type) (list '%cast
+                             (walk-type type)
+                             (walk-expr expr)))
+    (('enum . _) (walk-enum form))
+    ;; | is problematic... And c-or/bit-or/etc are actually
+    ;; procedures, so we have to call the procedure itself
+    (('c-or . rest) (apply c-or (map walk-expr rest)))
+    (('c-bit-or . rest) (apply c-bit-or (map walk-expr rest)))
+    (('c-bit-or= . rest) (apply c-bit-or= (map walk-expr rest)))
+    (else (map walk-expr form))))
 
-   ;; atom (hopefully)
-   ((not (list? form)) (cons (atom-to-fmt-c form) acc))
+(define (walk-var form)
+  ;; (var a int) -> (%var int a)
+  ;; (var a (const int) 32) -> (%var (const int) a 32)
+  ;; (var b [const char 512]) -> (%var (%array (const char) 512) b)
+  ;; note: [...] is actually (¤ ...) after reading
+  ;; (var c (fn ((int) (float)) void)) -> (%var (%fun void ((int) (float))) c)
+  `(%var
+    ,(walk-type (third form))
+    ,(atom-to-fmt-c (second form))
+    .
+    ,(if (null? (drop form 3))
+         (list)
+         (walk-expr (drop form 3)))      ; optional init expression
+    ))
 
-   ;; another special case - field access
-   ((and (symbol? (car form))
-         (char=? #\. (string-ref (symbol->string (car form)) 0)))
-    (cons (make-field-access form) acc))
+(define (walk-type form)
+  ;; int -> int
+  ;; (const int) -> const int
+  ;; [const char 512] ->(¤ (const char) 512) -> (%array (const char) 512)
+  ;; [float 8] -> (%array float 8)
+  ;; (* const char) -> (const char *)
+  ;; (const * const * const char) -> (const char * const * const)
+  ;; (fn ((int) (float)) void) -> (%fun void ((int) (float)))
+  (match form
+    (('¤ . array-type)
+     (if (integer? (last array-type))
+         ;; sized array
+         (let* ((type-list (drop-right array-type 1))
+                (type (maybe-unwrap-type type-list))
+                (size (last array-type)))
+           `(%array ,(walk-type type)
+                    ,size))
+         ;; sugar for pointer... Do we really need it? Guess why not,
+         ;; it's a strong semantic cue
+         `(%array ,(walk-type (maybe-unwrap-type array-type)))))
+    (('fn arglist ret-type)
+     `(%fun ,(walk-type ret-type) ,(walk-arglist arglist)))
+    (('fn . _)
+     (assert #f "Malformed function type form"))
 
-   ;; toplevel, or a start of a regular list form
-   (else
-    (let ((new-acc (list)))
-      (cons (fold-right
-             walk-generic
-             new-acc
-             form)
-            acc)))))
+    ;; Special case: nested structs/unions
+    ((or ('struct . _)
+         ('union . _)) (walk-struct form))
 
-(define (normalize-fn-form form)
+    (('enum . _) (walk-enum form))
+    (else
+     (type-convert-to-c form))))
+
+(define (type-convert-to-c type)
+  ;; Our pointers to C pointers
+  ;; int -> int
+  ;; * const char -> const char *
+  ;; const * const char -> const char * const
+  (if (atom? type) (atom-to-fmt-c type)
+      (flatten
+       (tree-map atom-to-fmt-c
+                 (flatten
+                  (list-join (reverse (list-split type '*))
+                             '(*)))))))
+
+(define (walk-fn-def form)
+  (match form
+    (('fn name args ret-type . maybe-body)
+     `(%fun
+       ,(walk-type ret-type)
+       ,(atom-to-fmt-c name)
+       ,(walk-arglist args)
+       .
+       ,(walk-expr maybe-body)))))
+
+;;; TODO: isn't there a better way?
+(define (is-probably-type form)
+  (case (car form)
+    ((¤ * const volatile struct union) #t)
+    (else #f)))
+
+(define (walk-arglist form)
+  ;; E.g.:
+  ;; ((float) (int) (const char) (* const char) (¤ (* const struct res) 32))
+  ;; ((f1 float) (f2 float) (f3 float) (res (¤ float 4)))
+  (map (fn
+        (match x
+          (('¤ . _) (walk-type x))
+
+          ;; yeah shitty, but I don't know yet how to determine if the
+          ;; first entry is part of the type and not an argument name
+          ;; :(
+          ((? is-probably-type) (walk-type x))
+
+          ;; 1 element args are always type
+          ((_) (walk-type x))
+
+          ((var . type) (append (list (walk-type (maybe-unwrap-type type)))
+                                (list (walk-type var))))))
+       form))
+
+(define (walk-function form)
   ;; (fn ret-type name arglist body) -> normal function
   ;; (fn ret-type name arglist) -> prototype
   (if (>= (length form) 5)
-      form
-      (cons 'prototype (cdr form))))
+      (walk-fn-def form)
+      (cons '%prototype (cdr (walk-fn-def form)))))
 
-(define (walk-function form static)
-  (if static
-      (walk-generic (list 'static (normalize-fn-form form))
-                    (list))
-      (walk-generic (normalize-fn-form (cdr form))
-                    (list))))
+(define (process-struct-fields fields)
+  (map (fn
+        (let ((type (walk-type (last x))))
+          (cons type (map atom-to-fmt-c (drop-right x 1)))))
+       fields))
+
+(define (walk-struct form)
+  (match form
+    ((type (fields ...) . attrs)        ; anonymous struct
+     `(,type ,(process-struct-fields fields)
+             . ,(tree-map atom-to-fmt-c attrs)))
+    ((type name)                        ; simple 'struct whatever', like in variable def
+     `(,type ,(atom-to-fmt-c name)))
+    ((type name (fields ...) . attrs)
+     `(,type ,(atom-to-fmt-c name)
+             ,(process-struct-fields fields)
+             . ,(tree-map atom-to-fmt-c attrs)))
+    (else (error "Malformed aggregate definition " form))))
+
+(define (walk-enum form)
+  (match form
+    (('enum (values ...))
+     `(enum ,(map atom-to-fmt-c values)))
+    (('enum name (values ...))
+     `(enum ,(atom-to-fmt-c name) ,(map atom-to-fmt-c values)))))
 
 (define (walk-extern form)
-  (case (cadr form)
-    ((fn)
-     (list (cons 'extern (walk-function form #f))))
-    ((var)
-     (list (cons 'extern (walk-generic (cdr form) (list)))))
+  (match form
+    (('fn . _)
+     ;; extern function?.. What
+     (list 'extern (walk-function form)))
+    (('var . _)
+     (list 'extern (walk-var form)))
     (else (error "Extern what?"))))
 
 (define (walk-public form)
-  (case (cadr form)
-    ((fn)
-     (walk-function form #f))
-    ((var)
-     (walk-generic (list 'static (cdr form)) (list)))
-    ((define defmacro import include struct typedef union var)
+  (match form
+    (('fn . _)
+     (walk-function form))
+    (('var . _)
+     (walk-var form))
+    ((or ('define . _)
+         ('defmacro . _)
+
+         ('import . _)
+         ('include . _)
+
+         ('struct . _)
+         ('union . _)
+
+         ('typedef . _))
      ;; ignore here, used in generating public interface
-     (process-toplevel-form (cdr form)))
+     (process-toplevel-form form))
     (else
      (error "Pub what?" (cadr form)))))
 
 (define (process-toplevel-form form)
-  ;; todo: rewrite to match
-  (case (car form)
-    ((fn) (walk-function form #t))
-    ((extern) (walk-extern form))
-    ((pub) (walk-public form))
-    (else (walk-generic form (list)))))
+  (match form
+    (('fn . _) (list 'static (walk-function form)))
+    (('var . _) (list 'static (walk-var form)))
+    (('extern . rest) (walk-extern rest))
+    (('pub . rest) (walk-public rest))
+    ((or ('struct . _)
+         ('union . _)) (walk-struct form))
+    (('enum . _) (walk-enum form))
+    (('define name . rest) `(%define ,(atom-to-fmt-c name) ,@rest))
+    (else (walk-expr form))))
+
+(define (get-line-num form)
+  (let ((num (get-line-number form)))
+    (if (string? num)
+        (last (string-split num ":"))
+        #f)))
+
+(define sex-fmt-current-file (make-parameter "/dev/null"))
+(define sex-fmt-line-num (make-parameter 0))
+
+(define (line-directive-string)
+  (fmt #f #\# "line " (sex-fmt-line-num) " " #\" (sex-fmt-current-file) #\"))
 
 (define (emit-c sex-forms)
   (for-each (lambda (form)
-              (fmt #t (c-expr (car (process-toplevel-form form))) nl))
+              (let ((start-line (get-line-num form)))
+                (when start-line
+                  (sex-fmt-line-num start-line)
+                  (fmt #t (line-directive-string) nl)))
+              (fmt #t (c-expr (process-toplevel-form form)) nl))
             sex-forms))

fmt-c.scm

@@ -9,6 +9,7 @@
 (declare (unit fmt-c))
 
 (import fmt
+        srfi-1
         srfi-13)
 
 (define (fmt-in-macro? st) (fmt-ref st 'in-macro?))
@@ -84,7 +85,8 @@
 (define (c-maybe-paren op x)
   (lambda (st)
     ((fmt-let 'op op
-              (if (c-op<= (fmt-op st) op)
+              (if (and (c-op<= (fmt-op st) op)
+                       (not (vector? st)))
                   (c-paren x)
                   x))
      st)))
@@ -557,10 +559,13 @@
 ;; data structures
 
 (define (c-struct/aux type x . o)
+  ;; can be just pointer to SUC, need to support such case:
+  ;; struct whatever * - body is just '*'
   (let* ((name (if (null? o) (if (or (symbol? x) (string? x)) x #f) x))
          (body (if name (if (not (null? o)) (car o) '()) x))
          (o (if (null? o) o (cdr o))))
-    (if (not (null? body))
+    (if (and (not (null? body))
+             (not (eq? '* body)))
         (c-wrap-stmt
          (cat
           (c-braced-block
@@ -572,7 +577,13 @@
                  (c-wrap-stmt (c-expr body))))))
           (if (pair? o) (cat " " (apply c-begin o)) (dsp ""))))
         (c-wrap-stmt
-         (cat type (if (and name (not (equal? name ""))) (cat " " name) ""))))))
+         (cat type
+              (if (and name (not (equal? name "")))
+                  (cat " " name)
+                  "")
+              (if (not (null? body))
+                  (cat body)
+                  ""))))))
 
 (define (c-struct . args) (apply c-struct/aux "struct" args))
 (define (c-union . args) (apply c-struct/aux "union" args))
@@ -597,9 +608,11 @@
 
 (define (c-while check . body)
   (c-reset-newline
-   (cat (c-block (cat "while (" (c-in-test (c-expr check)) ")")
-                 (c-in-stmt (apply c-begin body)))
-        fl)))
+   (if (null? body)
+       (cat "while (" (c-in-test (c-expr check)) ");")
+       (cat (c-block (cat "while (" (c-in-test (c-expr check)) ")")
+                     (c-in-stmt (apply c-begin body)))
+            fl))))
 
 (define (c-for init check update . body)
   (c-reset-newline
@@ -614,7 +627,7 @@
 (define (c-param x)
   (cond
     ((procedure? x) x)
-    ((pair? x) (c-type (car x) (cadr x)))
+    ((pair? x) (c-param-type (car x) (cadr x)))
     (else (error "missing type" x))))
 
 (define (c-field x)
@@ -688,6 +701,33 @@
      (else
       (cat (if (eq? '%pointer type) '* type) (if name (cat " " name) ""))))))
 
+(define (c-param-type type . o)
+  (let ((name (and (pair? o) (car o))))
+    (cond
+     ((pair? type)
+      (case (car type)
+        ((%fun)
+         (cat (c-type (cadr type) #f)
+              " (*" (or name "") ")("
+              (fmt-join (lambda (x) (c-type x #f)) (caddr type) ", ") ")"))
+        ((%array)
+         (let ((name (cat name "[" (if (pair? (cddr type))
+                                       (c-expr (caddr type))
+                                       "")
+                          "]")))
+           (c-type (cadr type) name)))
+        ((%pointer *)
+         (let ((name (cat "*" (if name (c-expr name) ""))))
+           (c-type (cadr type)
+                   (if (and (pair? (cadr type)) (eq? '%array (caadr type)))
+                       (c-paren name)
+                       name))))
+        (else (fmt-join/last c-expr (lambda (x) (c-type x name)) type " "))))
+     ((not type)
+      (lambda (st) ((c-type (or (fmt-default-type st) 'int) name) st)))
+     (else
+      (cat (if (eq? '%pointer type) '* type) (if name (cat " " name) ""))))))
+
 (define (c-var type name . init)
   (c-wrap-stmt
    (if (pair? init)

semen.scm

@@ -2,7 +2,8 @@
 
 (declare (unit semen)
          (uses sex-macros
-               sex-modules))
+               sex-modules
+               utils))
 
 (import
   (chicken string)
@@ -53,13 +54,16 @@
          ('pub 'fn . _)
          ('extern 'fn . _)) (process-fn sex-form acc))
     ((or ('struct . _)
-         ('pub struct . _)) (process-struct sex-form acc))
+         ('pub 'struct . _)) (process-struct sex-form acc))
     ((or ('union . _)
          ('pub 'union . _)) (process-struct sex-form acc))
+    ((or ('enum . _)
+         ('pub 'enum . _)) (process-struct sex-form acc))
     ((or ('var . _)
          ('pub 'var . _)
          ('extern 'var . _)) (process-global-var sex-form acc))
     (('include _) (cons sex-form acc))
+    (('define . _) (cons sex-form acc))
 
     (('import . modules)
      (semen-process-imports (get-public-forms modules) acc))
@@ -67,6 +71,10 @@
     ((or ('defmacro . rest)
          ('pub 'defmacro . rest)) (defmacro rest) acc)
 
+    ((or ('typedef new-type target)
+         ('pub 'typedef new-type target))
+     (process-typedef new-type target acc))
+
     (else (assert #f (fmt #f "Unknown top level form " sex-form)))))
 
 (define (semen-process-imports module-public-forms acc)
@@ -83,33 +91,46 @@
                                       acc))))))
 
 (define (semen-macro-expand form)
-  "Walk the form recursively and expand all macros, unitl none is left."
+  "Walk the form recursively and expand all macros, until none is left."
   (semen-walk-form
    form
    (lambda (subform env)
      (if (sex-macro? subform)
-         (apply-macro subform)
+         (cons semen-walk-embed-result (semen-apply-macro subform (list)))
          subform))
    #f))
 
-;;; TODO: for greater inspiration, see SBCL's walk.lisp and their
-;;; template system. Maybe it is worth it to implement something
-;;; similar here
+;;; semen-walk-form and friends: form walker with various abilities.
+;;; By default, replaces walked form with walk-fn result But may
+;;; perform additional operations depending of what the walk function
+;;; has requested.
+
+;;; For inspiration, see SBCL's walk.lisp and their template
+;;; system.
+
+(define semen-walk-embed-result (gensym)
+  ;; For cases when result is a list which must be embedded in the
+  ;; form, e.g. when it returned from a macro
+  )
+
 (define (semen-walk-form form walk-fn env)
   (if (atom? form) form
       (let ((new-form (walk-fn form env)))
         (cond ((not (eq? form new-form))
                (semen-walk-form new-form walk-fn env))
-              (else (recons
-                     new-form
-                     (semen-walk-form (car new-form) walk-fn env)
-                     (semen-walk-form (cdr new-form) walk-fn env)))))))
+              (else
+               (let ((new-car (semen-walk-form (car new-form) walk-fn env))
+                     (new-cdr (semen-walk-form (cdr new-form) walk-fn env)))
+                 (cond ((and (pair? new-car)
+                             (eq? (car new-car) semen-walk-embed-result))
+                        (append (cdr new-car) new-cdr))
+                       (else
+                        (recons new-form new-car new-cdr)))))))))
 
-(define (recons old-cons new-car new-cdr)
-  (if (and (eq? new-car (car old-cons))
-           (eq? new-cdr (cdr old-cons)))
-      old-cons
-      (cons new-car new-cdr)))
+;;; Typdef
+
+(define (process-typedef new-type target acc)
+  (cons `(typedef ,target ,new-type) acc))
 
 ;;; Fn processing
 
@@ -153,7 +174,7 @@
      (process-fn `(fn ,ret-type ,name ,arglist ,@body) (list)))
     (else (assert #f (fmt #f "Malformed lambda " form)))))
 
-;;; Struct
+;;; Structs
 
 (define (process-struct sex-struct acc)
   (cons sex-struct acc))

sex-reader.scm

@@ -2,12 +2,19 @@
 
 (include "utils.macros.scm")
 
-(import (chicken pathname)
-        brev-separate
-        fmt)
+(import
+  (chicken base)
+  (chicken io)
+  (chicken pathname)
+  (chicken port)
+  (chicken read-syntax)
+  (chicken string)
+  (chicken syntax)
+  brev-separate
+  fmt)
 
 (define (read-forms acc)
-  (let ((r (read)))
+  (let ((r (read-with-source-info (current-input-port))))
     (if (eof-object? r) (reverse acc)
         (read-forms (cons r acc)))))
 
@@ -16,7 +23,41 @@
     (with-input-from-file (pathname-strip-directory file)
       (fn (read-forms (list))))))
 
+(define (read-bracket port)
+  (let loop ((c (read-char port))
+             (str (string)))
+    (cond ((char=? c #\])
+           (cons '¤
+                 (with-input-from-string str
+                   (fn (port-map identity read)))))
+          ((char=? c #\[)
+           (loop port (conc )))
+          (else
+           (loop (read-char port)
+                 (conc str c))))))
+
+(define open-bracket-counter (make-parameter 0))
+
 (define (read-raw-forms input-source)
+  (let ((bracket-end (gensym)))
+   (set-read-syntax!
+    #\]
+    (lambda (port)
+      (when (= 0 (open-bracket-counter))
+        (error "Unmatched closing bracket"))
+      (open-bracket-counter (- (open-bracket-counter) 1))
+      bracket-end))
+
+   (set-read-syntax!
+    #\[
+    (lambda (port)
+      (open-bracket-counter (+ (open-bracket-counter) 1))
+      (let loop ((r (read port))
+                 (acc (list)))
+        (if (eq? r bracket-end)
+            (cons '¤ (reverse acc))
+            (loop (read port)
+                  (cons r acc)))))))
   (if (eq? input-source 'stdin)
       (read-forms (list))
       (read-from-file input-source)))

sexc.scm

@@ -1,6 +1,7 @@
 (declare (unit sexc)
          (uses fmt-c-writer
                sex-reader
+               utils
                semen))
 
 (include "utils.macros.scm")
@@ -117,6 +118,18 @@
       (with-directory input-source
         (semen-process raw-forms))))
 
+(define prelude
+  '((include inttypes.h)
+
+    (typedef u8 uint8-t)
+    (typedef i8 int8-t)
+    (typedef u16 uint16-t)
+    (typedef i16 int16-t)
+    (typedef u32 uint32-t)
+    (typedef i32 int32-t)
+    (typedef u64 uint64-t)
+    (typedef i64 int64-t)))
+
 (define (main)
   (let* ((raw-args (command-line-arguments))
          (args (getopt-long raw-args
@@ -142,7 +155,8 @@
          (return #f))
        (load-persistent-module-paths)
 
-       (let* ((raw-forms (read-raw-forms input))
+       (sex-fmt-current-file (to-absolute-pathname input))
+       (let* ((raw-forms (append prelude (read-raw-forms input)))
               (sex-forms (semantic-process-forms raw-forms input)))
          (if (or (get-arg args 'macro-expand #f)
                  (get-arg args 'emit-c #f))

tests/basic.scm

@@ -1,35 +1,31 @@
-(test-begin "basic")
+(test-group "basic"
 
-;;; unkebabify
-(test '- (unkebabify '-))
-(test '-- (unkebabify '--))
-(test '-> (unkebabify '->))
-(test '-= (unkebabify '-=))
-(test 'kebab_case (unkebabify 'kebab-case))
-(test '_what_ (unkebabify '-what-))
-(test 'this->member (unkebabify 'this->member))
-(test '_this_->_member_ (unkebabify '-this-->-member-))
-(test '__->>> (unkebabify '--->>>))
+  ;; unkebabify
+  (test '- (unkebabify '-))
+  (test '-- (unkebabify '--))
+  (test '-> (unkebabify '->))
+  (test '-= (unkebabify '-=))
+  (test 'kebab_case (unkebabify 'kebab-case))
+  (test '_what_ (unkebabify '-what-))
+  (test 'this->member (unkebabify 'this->member))
+  (test '_this_->_member_ (unkebabify '-this-->-member-))
+  (test '__->>> (unkebabify '--->>>))
 
-;;; atom-to-fmt-c
-(test '%fun (atom-to-fmt-c 'fn))
-(test '%prototype (atom-to-fmt-c 'prototype))
-(test '%var (atom-to-fmt-c 'var))
-(test '%block-begin (atom-to-fmt-c 'begin))
-(test '%define (atom-to-fmt-c 'define))
-(test '%pointer (atom-to-fmt-c 'pointer))
-(test '%array (atom-to-fmt-c 'array))
-(test 'vector-ref (atom-to-fmt-c '@))
-(test '%include (atom-to-fmt-c 'include))
-(test '%cast (atom-to-fmt-c 'cast))
+  ;; atom-to-fmt-c
+  (test '%fun (atom-to-fmt-c 'fn))
+  (test '%prototype (atom-to-fmt-c 'prototype))
+  (test '%block-begin (atom-to-fmt-c 'begin))
+  (test '%define (atom-to-fmt-c 'define))
+  (test '%pointer (atom-to-fmt-c 'pointer))
+  (test '%array (atom-to-fmt-c 'array))
+  (test 'vector-ref (atom-to-fmt-c '¤))
+  (test '%include (atom-to-fmt-c 'include))
 
-;;; c89 stuff
-(test 'int (atom-to-fmt-c 'bool))
-(test 1 (atom-to-fmt-c 'true))
-(test 0 (atom-to-fmt-c 'false))
+  ;; c89 stuff
+  (test 'int (atom-to-fmt-c 'bool))
+  (test 1 (atom-to-fmt-c 'true))
+  (test 0 (atom-to-fmt-c 'false))
 
-;;; make-field-access
-(test 'a.b (make-field-access '(.b a)))
-(test 'a.b.c (make-field-access '(.c a.b)))
-
-(test-end)
+  ;; make-field-access
+  (test 'a.b (make-field-access '(.b a)))
+  (test 'a.b.c (make-field-access '(.c a.b))))

tests/fmt-c-writer.scm

@@ -0,0 +1,159 @@
+;;; Types
+(test-group "fmt-writer"
+
+  (test
+   '(const int)
+   (walk-type '(const int)))
+
+  (test
+   '(%array (const char) 512)
+   (walk-type '(¤ const char 512)))
+
+  (test
+   '(%array (float) 512)
+   (walk-type '(¤ (float) 512)))
+
+  (test
+   '(%array (const char) 512)
+   (walk-type '(¤ (const char) 512)))
+
+  (test
+   '(%array (const char))
+   (walk-type '(¤ const char)))
+
+  (test
+   '(%array (const char))
+   (walk-type '(¤ (const char))))
+
+  (test
+   '(%array float 8)
+   (walk-type '(¤ float 8)))
+
+  (test
+   "Pointer to const char"
+   '(const char *)
+   (walk-type '(* const char)))
+
+  (test
+   "Const pointer to const char"
+   '(const char * const)
+   (walk-type '(const * const char)))
+
+  (test
+   '(%fun void ((int) (float) (%array (struct what * const))))
+   (walk-type '(fn ((int) (float) (¤ (const * struct what))) void)))
+
+  (test
+   '(%fun void ((int) (%array float) (%array (struct what * const))))
+   (walk-type '(fn ((int) (¤ float) (¤ (const * struct what))) void)))
+
+  (test
+   '(%array (%fun void ((int) (%array float) (%array (struct what * const)))))
+   (walk-type '(¤ (fn ((int) (¤ float) (¤ (const * struct what))) void))))
+
+  ;; Type convert to C
+  (test
+   '(int)
+   (type-convert-to-c '(int)))
+
+  (test
+   '(* int)
+   (type-convert-to-c '(int *)))
+
+  (test
+   '(* const int)
+   (type-convert-to-c '(const int *)))
+
+  (test
+   '(const * const char)
+   (type-convert-to-c '(const char * const)))
+
+;;; Variable defs
+  (test
+   '(%var (%array float 8) a)
+   (walk-var '(var a (¤ float 8))))
+
+  (test
+   '(%var (int *) a (& n))
+   (walk-var '(var a (* int) (& n))))
+
+  (test
+   '(%var (const int *) a (& n))
+   (walk-var '(var a (* const int) (& n))))
+
+  (test
+   '(%var (struct suc) s)
+   (walk-var '(var s (struct suc))))
+
+  (test
+   '(%var (const struct suc *) s s1)
+   (walk-var '(var s (* const struct suc) s1)))
+
+  (test
+   '(%var (const struct suc *) s s1)
+   (walk-var '(var s (* (const struct suc)) s1)))
+
+  (test
+   '(%var (struct suc) s (hoge piyo))
+   (walk-var '(var s (struct suc) (hoge piyo))))
+
+  (test
+   '(%var (struct suc *) s (hoge piyo))
+   (walk-var '(var s (* struct suc) (hoge piyo))))
+
+;;; Fn defs
+  (test
+   '(%fun void puk ((int) (%array float 8)))
+   (walk-fn-def '(fn puk ((int) (¤ float 8)) void)))
+
+  (test
+   '(%fun int main ((int argc) ((%array (const char)) argv))
+          (return 0))
+   (walk-fn-def
+    '(fn main ((argc int) (argv (¤ const char))) int
+         (return 0))))
+  (test
+   '(%fun int quxu (((struct piq *) bar))
+          (return 0))
+   (walk-fn-def
+    '(fn quxu ((bar (* struct piq))) int
+         (return 0))))
+
+  (test
+   '(%fun int quxu (((struct piq *) bar) ((%array (struct tt *)) ploop))
+          (return 0))
+   (walk-fn-def
+    '(fn quxu ((bar (* struct piq)) (ploop (¤ * struct tt))) int
+         (return 0))))
+
+  ;; Structs
+  (test
+   '(struct no_kebab ((int a) (float f)))
+   (walk-struct '(struct no-kebab ((a int) (f float)))))
+
+  (test
+   '(struct settings ((u32 x y w h)
+                      ((%array (struct ((float r g b a))) 4) colors)))
+   (walk-struct
+    '(struct settings
+             ((x y w h u32)
+              (colors [¤ struct ((r g b a float)) 4])))))
+
+  (test
+   '(struct settings ((u32 x y w h)
+                      ((%array (struct color ((float r g b a))) 4) colors)))
+   (walk-struct
+    '(struct settings
+             ((x y w h u32)
+              (colors [¤ struct color ((r g b a float)) 4])))))
+
+  (test
+   '(struct mega_kebab ((int a)
+                        ((struct ((int year) (int month) (int day))) dob)
+                        ((%fun int ((int) (%array int))) min)))
+   (walk-struct '(struct mega-kebab
+                         ((a int)
+                          (dob (struct ((year int)
+                                        (month int)
+                                        (day int))))
+                          (min (fn ((int) (¤ int)) bool)))))))

tests/reader.scm

@@ -0,0 +1,17 @@
+(import (chicken port))
+
+(define-syntax reader-test
+  (syntax-rules ()
+    ((reader-test result string)
+     (test result
+           (with-input-from-string string
+             (lambda () (read-raw-forms 'stdin)))))))
+
+(test-group "reader"
+  ;; []-syntax. For array types and array access expressions
+  (reader-test '((¤ * char)) "[* char]")
+  (reader-test '((¤ * * char const 512)) "[* * char const 512]")
+  (reader-test '((¤)) "[]")
+  (reader-test '((¤ (¤))) "[[]]")
+  (reader-test '((¤ (¤ const char))) "[[const char]]")
+)

tests/run.scm

@@ -9,6 +9,9 @@
 
 (include "basic.scm")
 (include "semen.scm")
+(include "reader.scm")
+(include "fmt-c-writer.scm")
+(include "utils.scm")
 
 ;;; Should be the last in the test suite
 (test-exit)

tests/semen.scm

@@ -1,3 +1,5 @@
+(import srfi-69)
+
 (define print-str-fn
   '(fn void print-str ((string s))
        (printf "%s" s)))
@@ -6,48 +8,49 @@
   '(pub fn float sum ((int a) (int b))
         (return (cast float (+ a b)))))
 
-(test-begin "semen")
-(test-assert (sex-fn? print-str-fn))
-(test #f (sex-fn-public? print-str-fn))
-(test 'void (sex-fn-return-type print-str-fn))
-(test 'print-str (sex-fn-name print-str-fn))
-(test '((string s)) (sex-fn-arglist print-str-fn))
-(test '(fn void print-str ((string s))) (sex-fn-prototype print-str-fn))
-(test '((printf "%s" s)) (sex-fn-body print-str-fn))
+(test-group "semen"
+  (test-assert (sex-fn? print-str-fn))
+  (test #f (sex-fn-public? print-str-fn))
+  (test 'void (sex-fn-return-type print-str-fn))
+  (test 'print-str (sex-fn-name print-str-fn))
+  (test '((string s)) (sex-fn-arglist print-str-fn))
+  (test '(fn void print-str ((string s))) (sex-fn-prototype print-str-fn))
+  (test '((printf "%s" s)) (sex-fn-body print-str-fn))
 
-(test-assert (sex-fn? sum-fn))
-(test #t (sex-fn-public? sum-fn))
-(test 'float (sex-fn-return-type sum-fn))
-(test 'sum (sex-fn-name sum-fn))
-(test '((int a) (int b)) (sex-fn-arglist sum-fn))
-(test '(pub fn float sum ((int a) (int b))) (sex-fn-prototype sum-fn))
-(test '((return (cast float (+ a b)))) (sex-fn-body sum-fn))
+  (test-assert (sex-fn? sum-fn))
+  (test #t (sex-fn-public? sum-fn))
+  (test 'float (sex-fn-return-type sum-fn))
+  (test 'sum (sex-fn-name sum-fn))
+  (test '((int a) (int b)) (sex-fn-arglist sum-fn))
+  (test '(pub fn float sum ((int a) (int b))) (sex-fn-prototype sum-fn))
+  (test '((return (cast float (+ a b)))) (sex-fn-body sum-fn))
 
-(let ((sex-code
-       '((defmacro (sum-var name a b c)
-           `(var ,name ,(+ a b c)))
+  (let ((sex-code
+         '((defmacro (sum-var name a b c)
+             `(var ,name ,(+ a b c)))
 
-         (sum-var v 1 2 3))))
+           (sum-var v 1 2 3))))
 
-  (test '((var v 6)) (semen-process sex-code)))
+    (test '((var v 6)) (semen-process sex-code)))
 
 ;;; Macro expansion
 
-(test 'a (semen-walk-form 'a identity))
-(test '(a b c) (semen-walk-form '(a b c) identity))
+  (define (form-identity form env)
+    form)
 
-(test 'a (semen-macro-expand 'a))
-(test '(a b c) (semen-macro-expand '(a b c)))
+  (test 'a (semen-walk-form 'a form-identity (make-hash-table)))
+  (test '(a b c) (semen-walk-form '(a b c) form-identity (make-hash-table)))
 
-(let ((sex-code-macro
-       '((defmacro (x10 a)
-           `(* 10 ,a))
+  (test 'a (semen-macro-expand 'a))
+  (test '(a b c) (semen-macro-expand '(a b c)))
 
-         (fn void foo ((int a) (int b))
-             (return (+ a (x10 b)))))))
+  (let ((sex-code-macro
+         '((defmacro (x10 a)
+             `(* 10 ,a))
 
-  (test '((fn void foo ((int a) (int b))
-              (return (+ a (* 10 b)))))
-        (semen-process sex-code-macro)))
+           (fn void foo ((int a) (int b))
+               (return (+ a (x10 b)))))))
 
-(test-end)
+    (test '((fn void foo ((int a) (int b))
+                (return (+ a (* 10 b)))))
+          (semen-process sex-code-macro))))

tests/utils.scm

@@ -0,0 +1,22 @@
+(test-group "utils"
+
+  (test
+   '((1) (2) (3))
+   (list-split '(1 * 2 * 3) '*))
+
+  (test
+   '((1 2 3))
+   (list-split '(1 2 3) '*))
+
+  (test
+   '(() (1) (2) (3) ())
+   (list-split '(* 1 * 2 * 3 *) '*))
+
+  (test
+   '((const) (const struct something))
+   (list-split '(const * const struct something) '*))
+
+  (test
+   '(1 * 2 * 3)
+   (list-join '(1 2 3) '*))
+)

utils.scm

@@ -4,7 +4,8 @@
 
 (import
   (chicken pathname)
-  (chicken process-context))
+  (chicken process-context)
+  srfi-1)
 
 (define (get-env-var name)
   (get-environment-variable name))
@@ -17,3 +18,35 @@
         (make-absolute-pathname
          (current-directory)
          (pathname-directory file))))))
+
+(define (to-absolute-pathname pathname)
+  (if (absolute-pathname? pathname)
+      pathname
+      (make-absolute-pathname
+       (current-directory)
+       pathname)))
+
+(define (list-split src-list split-elt)
+  ;; split '(1 2 / 3 4 / 5 6) by '/ -> '((1 2) (3 4) (5 6))
+  (fold (lambda (elt acc)
+          (if (eq? elt split-elt)
+              (append acc (list (list)))
+              (append (drop-right acc 1)
+                      (list (append (last acc) (list elt))))))
+        (list (list))
+        src-list))
+
+(define (list-join lists join-by)
+  (drop-right
+   (fold (lambda (elt acc)
+           (append acc (list elt) (list join-by)))
+         (list)
+         lists)
+   1))
+
+;;; Reconstruct form
+(define (recons old-cons new-car new-cdr)
+  (if (and (eq? new-car (car old-cons))
+           (eq? new-cdr (cdr old-cons)))
+      old-cons
+      (cons new-car new-cdr)))