get the recursive descent framework worked out

janet/recursive.janet

@@ -31,7 +31,12 @@
  })
 
 ### and some helper functions for interfacing with that data structure
-(defn- current [parser] (get (parser :tokens) (parser :current)))
+(defn- current [parser] 
+ (def curr (get (parser :tokens) (parser :current)))
+ (if (not curr)
+  (error "no more tokens")
+  curr))
+
 
 (defn- peek [parser] (get (parser :tokens) (inc (parser :current))))
 
@@ -39,46 +44,110 @@
 
 (defn- type [token] (get token :type))
 
-(defn- expect [parser type]
+(defn- check [parser type]
  (def current-type (-> parser current (get :type)))
  (= type current-type))
 
 ### Parsing functions
-(declare expr)
+(declare nonbinding binding)
+
+# errors
+(def terminators [:break :newline :semicolon :eof])
+
+(defn- terminates? [parser]
+ (def curr (current parser))
+ (def ttype (type curr))
+ (has-value? terminators ttype))
+
+(defn- panic [parser message]
+ (print "Panic in the parser: " message)
+ (def origin (current parser))
+ (advance parser)
+ (def skipped @[origin])
+ (while (not (terminates? parser))
+  (array/push skipped (current parser))
+  (advance parser))
+ (array/push skipped (current parser))
+ (advance parser)
+ (error {:type :error :data skipped :token origin}))
+
+(defn- expected [parser ttype]
+ (panic parser (string "expected " ttype ", got " (-> parser current type))))
+
+(defn- expect [parser type]
+ (if-not (check parser type) (expected parser type)))
 
 # atoms
-(defn- bool [parser] 
+(defn- bool [parser]
+ (expect parser :bool)
  (def curr (-> parser current))
  (def ttype (type curr))
  (def value (if (= ttype :true) true false))
- (def ast {:type :bool :value value :token curr})
+ (advance parser)
- (update parser :ast array/push ast)
+ {:type :bool :data value :token curr}
- (advance parser))
+ )
 
 (defn- num [parser]
+ (expect parser :number)
  (def curr (-> parser current))
- (def ast {:type :number :value (curr :literal) :token curr})
+ (advance parser)
- (update parser :ast array/push ast)
+ {:type :number :data (curr :literal) :token curr}
- (advance parser))
+ )
 
 (defn- kw [parser]
+ (expect parser :keyword)
  (def curr (-> parser current))
- (def ast {:type :keyword :value (curr :literal) :token curr})
+ (advance parser)
- (update parser :ast array/push ast)
+ {:type :keyword :data (curr :literal) :token curr}
- (advance parser))
+ )
 
 (defn- nill [parser]
- (def ast {:type :nil :token (current parser)})
+ (expect parser :nil)
- (update parser :ast array/push ast)
+ (advance parser)
- (advance parser))
+ {:type :nil :token (current parser)}
+ )
 
 (defn- str [parser]
+ (expect parser :string)
  (def curr (-> parser current))
- (def ast {:type :string :value (curr :literal) :token curr})
+ (advance parser)
- (update parser :ast array/push ast)
+ {:type :string :data (curr :literal) :token curr}
- (advance parser))
+ )
 
-(defrec expr [parser]
+(def separates [:break :newline :comma])
+
+(defn- separates? [parser]
+ (def curr (current parser))
+ (def ttype (type curr))
+ (has-value? separates ttype))
+
+(defn- separators [parser]
+ (if-not (separates? parser) 
+  (panic parser (string "expected separator, got " (-> parser current type))))
+ (while (separates? parser) (advance parser)))
+
+(defn- tup-term [parser]
+ (def term (nonbinding parser))
+ (if (separates? parser)
+  (do
+   (while (separates? parser) (advance parser))
+   term)
+  (panic parser (string "expected separator, got " (type (current parser))))))
+
+(defn- tup [parser]
+ (def origin (current parser))
+ (advance parser) # consume the :lparen
+ (def ast {:type :tuple :data @[] :token origin})
+ (while (separates? parser) (advance parser)) # consume any separators
+ (while (not (check parser :rparen))
+  (def term (try (nonbinding parser) ([e] e)))
+  (array/push (ast :data) term)
+  (try (separators parser) 
+   ([e] (pp e) (array/push (ast :data) e))))
+ (advance parser)
+ ast)
+
+(defrec nonbinding [parser]
  (def curr (current parser))
  (case (type curr)
   # atoms
@@ -92,18 +161,30 @@
   :string (str parser)
   ### TODO: interpolated strings
 
+  # tuples
+  :lparen (tup parser)
+
+  (panic parser (string "expected nonbinding expression, got " (type curr)))
+ )
+)
+
+(defrec binding [parser]
+ (def curr (current parser))
+ (case (type curr)
+  :let nil
+  :fn nil
  )
 )
 
-(do
-#(comment
 (os/cd "janet") # For repl to do relative imports
 (import ./scanner :as s)
+(do
+#(comment
 
-(def scanned (s/scan "\"foo bar baz\""))
+(def scanned (s/scan "(1, (2 3), 3)"))
 (def a-parser (new-parser scanned))
-(def parsed (expr a-parser))
+(def parsed (nonbinding a-parser))
-(-> parsed (get :ast) (get 0) (get :value))
+(-> parsed (get :data) )
 )