implement thread macros

dasy/builtin/macros.hy

@@ -98,3 +98,32 @@
         (.append forms (.read dasy stream))
         (except [EOFError] (break))))
     `(splice ~@forms)))
+
+;; ->
+(defmacro arrow [args #*body]
+  ;; TODO: Get rid of this dynamic import
+  (import hy.models [Expression])
+  (let [first-exp (get body 0)
+        rest (cut body 1 None)
+        body (if (isinstance first-exp Expression)
+                 `(~(get first-exp 0) ~args ~@(cut first-exp 1 None))
+                 `(~first-exp ~args))]
+    (for [exp rest]
+      (setv body (if (isinstance exp Expression)
+                    `(~(get exp 0) ~body ~@(cut exp 1 None))
+                    `(~exp ~body))))
+    body))
+
+;; ->>
+(defmacro arroww [args #*body]
+  (import hy.models [Expression])
+  (let [first-exp (get body 0)
+        rest (cut body 1 None)
+        body (if (isinstance first-exp Expression)
+                 `(~(get first-exp 0) ~@(cut first-exp 1 None) ~args)
+                 `(~first-exp ~args))]
+    (for [exp rest]
+      (setv body (if (isinstance exp Expression)
+                    `(~(get exp 0) ~@(cut exp 1 None) ~body)
+                    `(~exp ~body))))
+    body))

dasy/parser/parse.py

@@ -35,6 +35,8 @@
     "*!": "unsafe_mul",
     "/!": "unsafe_div",
     "def": "annassign",
+    "->": "arrow",
+    "->>": "arroww",
 }
 
 SRC = ""

examples/simple_auction.dasy

@@ -25,7 +25,9 @@
   ;; auction start time can be in the past, present, or future
   (set self/auctionStart auction_start)
   ;; auction end time should be in the future
-  (set self/auctionEnd (+ self/auctionStart bidding_time)))
+  (->> bidding_time
+       (+ self.auctionStart)
+       (set self/auctionEnd)))
 
 ;; Bid on the auction with the value sent with the transaction
 ;; the value will only be refunded if the auction is not won
@@ -37,8 +39,9 @@
   ;; Check if bid is high enough
   (assert (> msg/value self/highestBid))
   ;; Track the refund for the previous highest bidder
-  (+= (subscript self/pendingReturns self/highestBidder) self/highestBid)
-  ;; (set (subscript self/pendingReturns self/highestBidder) (+ 1 (subscript self/pendingReturns self/highestBidder)))
+  (-> self/pendingReturns
+      (subscript self/highestBidder)
+      (+= self/highestBid))
   ;; Track new high bid
   (set self/highestBidder msg/sender)
   (set self/highestBid msg/value))