add support for begin in Sex

begin-wrapped blocks are now creating lexical scopes

example/list.sex

@@ -38,9 +38,10 @@
 
 (pub defmacro (list-for-each list-type list-var elt-type elt-var what-do)
   (let ((list-var-2 (cat list-var '-2)))
-    `((var (pointer ,list-type) ,list-var-2 ,list-var)
-      (var ,elt-type ,elt-var (-> ,list-var-2 value))
-      (while (!= (-> ,list-var-2 next) NULL)
-        ,what-do
-        (= ,list-var-2 (-> ,list-var-2 next))
-        (= ,elt-var (-> ,list-var-2 value))))))
+    `((begin
+       (var (pointer ,list-type) ,list-var-2 ,list-var)
+       (var ,elt-type ,elt-var (-> ,list-var-2 value))
+       (while (!= (-> ,list-var-2 next) NULL)
+         ,what-do
+         (= ,list-var-2 (-> ,list-var-2 next))
+         (= ,elt-var (-> ,list-var-2 value)))))))

fmt-c.scm

@@ -218,6 +218,7 @@
              ((apply cpp-if/aux (substring/shared (symbol->string (car x)) 1)
                      (cdr x)) st))
             ((%endif) ((apply cpp-endif (cdr x)) st))
+            ((%block-begin) ((apply c-braced-block #f (cdr x)) st))
             ((%block) ((apply c-braced-block (cdr x)) st))
             ((%comment) ((apply c-comment (cdr x)) st))
             ((:) ((apply c-label (cdr x)) st))
@@ -521,7 +522,7 @@
 
 (define (c-braced-block/aux offset header . body)
    (lambda (st)
-     ((cat header (c-open-brace st) (c-indent st offset)
+     ((cat (if header header "") (c-open-brace st) (c-indent st offset)
            (apply c-begin body) fl
            (c-current-indent-string st offset) (c-close-brace st))
       st)))

sexc.scm

@@ -36,7 +36,7 @@
     ((fn) '%fun)
     ((prototype) '%prototype)
     ((var) '%var)
-    ((begin) '%begin)
+    ((begin) '%block-begin)
     ((define) '%define)
     ((pointer) '%pointer)
     ((array) '%array)

tests/run.scm

@@ -21,7 +21,7 @@
 (test '%fun (atom-to-fmt-c 'fn))
 (test '%prototype (atom-to-fmt-c 'prototype))
 (test '%var (atom-to-fmt-c 'var))
-(test '%begin (atom-to-fmt-c 'begin))
+(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))