add @ prefix for splicing

brag/brag/codegen/codegen.rkt

@@ -230,13 +230,13 @@
                       [$n-end-pos (format-id (last translated-patterns) "$~a-end-pos" (length translated-patterns))])
           #`(positions->srcloc $1-start-pos $n-end-pos))))
 
-  ;; move 'splice property into function because name is datum-ized
+  ;; move 'hide-or-splice property into function because name is datum-ized
   (with-syntax ([(translated-pattern ...) translated-patterns]
                 [(translated-action ...) translated-actions])
     #`[(translated-pattern ...)
        (rule-components->syntax '#,rule-name/false translated-action ...
                                 #:srcloc #,whole-rule-loc
-                                #:splice? #,(syntax-property rule-name/false 'splice))]))
+                                #:hide-or-splice? #,(syntax-property rule-name/false 'hide-or-splice))]))
 
 
 

brag/brag/codegen/runtime.rkt

@@ -158,17 +158,19 @@ This would be the place to check a syntax property for hiding.
   (datum->syntax #f d (positions->srcloc start-pos end-pos) stx-with-original?-property))
 
 
-(define splice-signal '@)
 ;; rule-components->syntax: (U symbol false) (listof stx) ... #:srcloc (U #f (list src line column offset span)) -> stx
 ;; Creates an stx out of the rule name and its components.
 ;; The location information of the rule spans that of its components.
-(define (rule-components->syntax rule-name/false #:srcloc [srcloc #f] #:splice? [splice #f] . componentss)
+(define (rule-components->syntax rule-name/false #:srcloc [srcloc #f] #:hide-or-splice? [hide-or-splice #f] . componentss)
   (let ([spliced-componentss (append-map (λ(cs)
-                                   (if (and (pair? cs) (syntax-property (car cs) 'splice))
-                                            (list (list (syntax-case (car cs) ()
-                                                    [(rule-name c ...)
-                                                     #'(c ...)])))
-                                            (list cs))) componentss)])
+                                           (cond
+                                             [(and (pair? cs) (equal? (syntax-property (car cs) 'hide-or-splice) "hide"))
+                                              (list (list (syntax-case (car cs) ()
+                                                            [(rule-name c ...)
+                                                             #'(c ...)])))]
+                                             [(and (pair? cs) (equal? (syntax-property (car cs) 'hide-or-splice) "splice"))
+                                              (list (cdr (syntax->list (car cs))))]
+                                             [else (list cs)])) componentss)])
     (syntax-property
      (datum->syntax #f 
                     (cons
@@ -176,4 +178,4 @@ This would be the place to check a syntax property for hiding.
                      (apply append spliced-componentss))
                     srcloc
                     stx-with-original?-property)
-     'splice splice)))
+     'hide-or-splice hide-or-splice)))

brag/brag/examples/baby-json-hider.rkt

@@ -13,4 +13,4 @@ array: "[" [json ("," json)*] "]"
 
 object: !"{" [kvpair ("," kvpair)*] !"}"
 
-!kvpair : !ID ":" !json
+@kvpair : !ID ":" !json

brag/brag/rules/lexer.rkt

@@ -63,6 +63,8 @@
     (token-RULE_HEAD lexeme)]
    [(:: "!" id (:* whitespace) ":")
     (token-RULE_HEAD_HIDDEN lexeme)]
+   [(:: "@" id (:* whitespace) ":")
+    (token-RULE_HEAD_SPLICED lexeme)]
    [id
     (token-ID lexeme)]
    

brag/brag/rules/parser.rkt

@@ -18,6 +18,7 @@
          token-REPEAT
          token-RULE_HEAD
          token-RULE_HEAD_HIDDEN
+         token-RULE_HEAD_SPLICED
          token-ID
          token-LIT
          token-EOF
@@ -47,6 +48,7 @@
                        REPEAT
                        RULE_HEAD
                        RULE_HEAD_HIDDEN
+                       RULE_HEAD_SPLICED
                        ID
                        LIT
                        EOF))
@@ -88,7 +90,7 @@
                       #f)
               $2))]
      
-     ;; bang indicates hiding. set hide value to #t
+     ;; bang indicates hiding. set hide value to "hide"
      [(RULE_HEAD_HIDDEN pattern)
       (begin
         (define trimmed (cadr (regexp-match #px"!(\\S+)\\s*:$" $1)))
@@ -100,7 +102,22 @@
                            (position-line $1-start-pos)
                            (position-col $1-start-pos))
                       trimmed
-                      #t)
+                      "hide") ; symbols won't work for these signals
+              $2))]
+     
+     ;; atsign indicates splicing. set hide value to "splice"
+     [(RULE_HEAD_SPLICED pattern)
+      (begin
+        (define trimmed (cadr (regexp-match #px"@(\\S+)\\s*:$" $1)))
+        (rule (position->pos $1-start-pos)
+              (position->pos $2-end-pos)
+              (lhs-id (position->pos $1-start-pos)
+                      (pos (+ (position-offset $1-start-pos)
+                              (string-length trimmed))
+                           (position-line $1-start-pos)
+                           (position-col $1-start-pos))
+                      trimmed
+                      "splice") 
               $2))]]
     
     [pattern

brag/brag/rules/stx.rkt

@@ -33,7 +33,7 @@
                               (- (pos-offset (lhs-id-end (rule-lhs a-rule)))
                                  (pos-offset (lhs-id-start (rule-lhs a-rule))))
                               #f)))
-     'splice (lhs-id-splice (rule-lhs a-rule))))
+     'hide-or-splice (lhs-id-splice (rule-lhs a-rule))))
   (define pattern-stx (pattern->stx source (rule-pattern a-rule)))
   (define line (pos-line (rule-start a-rule)))
   (define column (pos-col (rule-start a-rule)))

brag/brag/test/test-baby-json-hider.rkt

@@ -10,7 +10,7 @@
                ":"
                (token 'STRING "'hello world'")
                "}")))
- '(json (object (":"))))
+ '(json (object ":")))
 
 
 (check-equal?