fix nil parser bug, start work on patterns

janet/recursive.janet

@@ -161,16 +161,15 @@
 
 (defn- nill [parser]
  (expect parser :nil)
+ (def curr (current parser))
  (advance parser)
- {:type :nil :token (current parser)}
- )
+ {:type :nil :token curr})
 
 (defn- str [parser]
  (expect parser :string)
  (def curr (-> parser current))
  (advance parser)
- {:type :string :data (curr :literal) :token curr}
- )
+ {:type :string :data (curr :literal) :token curr})
 
 # words & synthetic expressions
 (def separates [:break :newline :comma])
@@ -311,6 +310,32 @@
  ast)
 
 ### patterns
+(declare pattern)
+
+(defn- placeholder [parser]
+ (expect parser :placeholder :ignored)
+ (def origin (current parser))
+ (advance parser)
+ {:type :placeholder :token origin})
+
+(defn- word-pattern [parser]
+ (expect parser :word)
+ (def origin (current parser))
+ (advance parser)
+ {:type :word :data (origin :lexeme) :token origin})
+
+(defrec pattern [parser]
+ (case (-> parser current type)
+  :nil (nill parser)
+  :true (bool parser)
+  :false (bool parser)
+  :keyword (kw parser)
+  :number (number parser)
+  :word (word-pattern parser)
+  :placeholder (placeholder parser)
+
+ )
+)
 
 ### conditional forms
 # if {simple} then {nonbinding} else {nonbinding}
@@ -338,6 +363,7 @@
  (while (terminates? parser) (advance parser)))
 
 # {simple} -> {nonbinding} {terminator}
+### TODO: add placeholder as valid lhs
 (defn- when-clause [parser]
  (try
   (do