[#48] parse '#?@' into ':reader-macro' node.

Author: Yannick Scherer

src/rewrite_clj/parser/core.clj

@@ -119,6 +119,24 @@
     \' (node/var-node (parse-printables reader :var 1 true))
     \= (node/eval-node (parse-printables reader :eval 1 true))
     \_ (node/uneval-node (parse-printables reader :uneval 1 true))
+    \? (do
+         ;; we need to examine the next character, so consume one (known \?)
+         (reader/next reader)
+         ;; we will always have a reader-macro-node as the result
+         (node/reader-macro-node
+          (let [read1 (fn [] (parse-printables reader :reader-macro 1))]
+            (cons (case (reader/peek reader)
+                    ;; the easy case, just emit a token
+                    \( (node/token-node (symbol "?"))
+
+                    ;; the harder case, match \@, consume it and emit the token
+                    \@ (do (reader/next reader)
+                           (node/token-node (symbol "?@")))
+
+                    ;; otherwise no idea what we're reading but its \? prefixed
+                    (do (reader/unread reader \?)
+                        (first (read1))))
+                  (read1)))))
     (node/reader-macro-node (parse-printables reader :reader-macro 2))))
 
 (defmethod parse-next* :deref

src/rewrite_clj/reader.clj

@@ -109,6 +109,11 @@
   [reader]
   (r/read-char reader))
 
+(defn unread
+  "Unreads a char. Puts the char back on the reader."
+  [reader ch]
+  (r/unread reader ch))
+
 (defn peek
   "Peek next char."
   [reader]

test/rewrite_clj/parser_test.clj

@@ -86,7 +86,7 @@
   "#=sym"                :eval             []              '(eval 'sym)
   "#=  sym"              :eval             [:whitespace]   '(eval 'sym)
   "#'sym"                :var              []              '(var sym)
-  "#'\nsym"              :var              [:newline])     '(var sym)
+  "#'\nsym"              :var              [:newline])
 
 (fact "about eval."
       (let [n (p/parse-string "#=(+ 1 2)")]
@@ -191,6 +191,9 @@
   "#=(+ 1 2)"                :eval            [:list]
   "#macro 1"                 :reader-macro    [:token :whitespace :token]
   "#macro (* 2 3)"           :reader-macro    [:token :whitespace :list]
+  "#?(:clj bar)"             :reader-macro    [:token :list]
+  "#?@(:clj bar)"            :reader-macro    [:token :list]
+  "#?foo baz"                :reader-macro    [:token :whitespace :token]
   "#_abc"                    :uneval          [:token]
   "#_(+ 1 2)"                :uneval          [:list]
   "#(+ % 1)"                 :fn              [:token :whitespace