From a5dce2c55e866c662c18e196f721417c57d101f9 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Sun, 10 Jun 2018 18:45:33 -0700
Subject: [PATCH] lex & parse the operator

---
 brag/rules/lexer.rkt  | 7 +++++--
 brag/rules/parser.rkt | 6 ++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/brag/rules/lexer.rkt b/brag/rules/lexer.rkt
index 8665142..b5a485e 100755
--- a/brag/rules/lexer.rkt
+++ b/brag/rules/lexer.rkt
@@ -64,8 +64,11 @@
     (token-SPLICE lexeme)]
    ["|"
     (token-PIPE lexeme)]
-   [(:or "+" "*")
-    (token-REPEAT lexeme)]
+   [(:or "+" "*"
+         ;; todo: consolidate next two patterns?
+         (:: "{" (:* digit) "}")
+         (:: "{" (:* digit) "," (:* digit) "}"))
+    (token-REPEAT (let () (println lexeme) lexeme))]
    [whitespace
     ;; Skip whitespace
     (return-without-pos (lex/1 input-port))]
diff --git a/brag/rules/parser.rkt b/brag/rules/parser.rkt
index 9d25117..05cfa9a 100755
--- a/brag/rules/parser.rkt
+++ b/brag/rules/parser.rkt
@@ -162,6 +162,12 @@
              (pattern-repeat (position->pos $1-start-pos)
                              (position->pos $2-end-pos)
                              1 $1)]
+            [(regexp-match #px"^\\{(\\d+)?,?(\\d+)?\\}$" $2)
+             => (λ (m)
+                  (define pr (match m
+                      [(list _ min max) (cons (and min (string->number min))
+                                                (and max (string->number max)))]))
+                  (error (format "~a" pr)))]
             [else
              (error 'grammar-parse "unknown repetition operator ~e" $2)])]
      [(atomic-pattern)