From 55c091e89800aee3e1a34ff68784fe846692b70e Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Sun, 23 Dec 2018 14:13:27 -0500
Subject: [PATCH] Update core.janet

---
 src/core/core.janet | 36 ++++++++++++++++++++++++++++++++++--
 src/core/fiber.c    |  2 +-
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/core/core.janet b/src/core/core.janet
index 7c4e5057..5f81334c 100644
--- a/src/core/core.janet
+++ b/src/core/core.janet
@@ -741,7 +741,7 @@
 
 (defmacro ->
   "Threading macro. Inserts x as the second value in the first form
-  in form, and inserts the modified firsts form into the second form
+  in forms, and inserts the modified first form into the second form
   in the same manner, and so on. Useful for expressing pipelines of data."
   [x & forms]
   (defn fop [last n]
@@ -754,7 +754,7 @@
 
 (defmacro ->>
   "Threading macro. Inserts x as the last value in the first form
-  in form, and inserts the modified firsts form into the second form
+  in forms, and inserts the modified first form into the second form
   in the same manner, and so on. Useful for expressing pipelines of data."
   [x & forms]
   (defn fop [last n]
@@ -765,6 +765,38 @@
     (tuple/slice parts 0))
   (reduce fop x forms))
 
+(defmacro -?>
+  "Short circuit threading macro. Inserts x as the last value in the first form
+  in forms, and inserts the modified first form into the second form
+  in the same manner, and so on. The pipeline will return nil
+  if an intermediate value is nil.
+  Useful for expressing pipelines of data."
+  [x & forms]
+  (defn fop [last n]
+    (def [h t] (if (= :tuple (type n))
+                 [tuple n.0 (array/slice n 1)]
+                 [tuple n @[]]))
+    (def sym (gensym))
+    (def parts (array/concat @[h sym] t))
+    ~(let [,sym ,last] (if ,sym ,(tuple/slice parts 0))))
+  (reduce fop x forms))
+
+(defmacro -?>>
+  "Threading macro. Inserts x as the last value in the first form
+  in forms, and inserts the modified first form into the second form
+  in the same manner, and so on. The pipeline will return nil
+  if an intermediate value is nil.
+  Useful for expressing pipelines of data."
+  [x & forms]
+  (defn fop [last n]
+    (def [h t] (if (= :tuple (type n))
+                 [tuple n.0 (array/slice n 1)]
+                 [tuple n @[]]))
+    (def sym (gensym))
+    (def parts (array/concat @[h] t @[sym]))
+    ~(let [,sym ,last] (if ,sym ,(tuple/slice parts 0))))
+  (reduce fop x forms))
+
 (defn partial
   "Partial function application."
   [f & more]
diff --git a/src/core/fiber.c b/src/core/fiber.c
index 31f9b6e3..f8f5e023 100644
--- a/src/core/fiber.c
+++ b/src/core/fiber.c
@@ -386,7 +386,7 @@ static const JanetReg cfuns[] = {
         "(fiber/new func [,sigmask])\n\n"
         "Create a new fiber with function body func. Can optionally "
         "take a set of signals to block from the current parent fiber "
-        "when called. The mask is specified as symbol where each character "
+        "when called. The mask is specified as a symbol where each character "
         "is used to indicate a signal to block. The default sigmask is :y. "
         "For example, \n\n"
         "\t(fiber/new myfun :e123)\n\n"