Add accumulate(2) and reduce2

These functions are variations on reduce and can be quite useful.
Improve error message for jpm as well.

CHANGELOG.md

@@ -2,6 +2,7 @@
 All notable changes to this project will be documented in this file.
 
 ## Unreleased
+- Add `reduce2`, `accumulate`, and `accumulate2`.
 - Add lockfiles to `jpm` via `jpm make-lockfile` and `jpm load-lockfile`.
 - Add `os/realpath` (Not supported on windows).
 - Add `os/chmod`.

auxbin/jpm

@@ -686,8 +686,8 @@ int main(int argc, const char **argv) {
   (def mdir (find-manifest-dir))
   (each man (os/dir mdir)
     (def package (parse (slurp (string mdir sep man))))
-    (if (or (not (package :repo)) (not (package :sha)))
-      (print "Cannot add local package " man " to lockfile, skipping...")
+    (if (or (not (dictionary? package)) (not (package :repo)) (not (package :sha)))
+      (print "Cannot add local or malformed package " mdir sep man " to lockfile, skipping...")
       (array/push packages package)))
   # Put in correct order, such that a package is preceded by all of its dependencies
   (def ordered-packages @[])

src/boot/boot.janet

@@ -699,6 +699,43 @@
   (each x ind (set res (f res x)))
   res)
 
+(defn reduce2
+  "The 2 argument version of reduce that does not take an initialization value.
+  Instead the first element of the array is used for initialization."
+  [f ind]
+  (var k (next ind))
+  (var res (in ind k))
+  (set k (next ind k))
+  (while (not= nil k)
+    (set res (f res (in ind k)))
+    (set k (next ind k)))
+  res)
+
+(defn accumulate
+  "Similar to reduce, but accumulates intermediate values into an array.
+  The last element in the array is what would be the return value from reduce.
+  The init value is not added to the array.
+  Returns a new array."
+  [f init ind]
+  (var res init)
+  (def ret (array/new (length ind)))
+  (each x ind (array/push ret (set res (f res x))))
+  ret)
+
+(defn accumulate2
+  "The 2 argument version of accumulate that does not take an initialization value."
+  [f ind]
+  (var k (next ind))
+  (def ret (array/new (length ind)))
+  (var res (in ind k))
+  (array/push ret res)
+  (set k (next ind k))
+  (while (not= nil k)
+    (set res (f res (in ind k)))
+    (array/push ret res)
+    (set k (next ind k)))
+  ret)
+
 (defn map
   "Map a function over every element in an indexed data structure and
   return an array of the results."

test/suite8.janet

@@ -181,4 +181,14 @@
   (def c (unmarshal (marshal b)))
   (assert (= 2 (c 1)) "marshal-on-stack-closure 1"))
 
+# Reduce2
+
+(assert (= (reduce + 0 (range 1 10)) (reduce2 + (range 10))) "reduce2 1")
+(assert (= (reduce * 1 (range 2 10)) (reduce2 * (range 1 10))) "reduce2")
+
+# Accumulate
+
+(assert (deep= (accumulate + 0 (range 5)) @[0 1 3 6 10]) "accumulate 1")
+(assert (deep= (accumulate2 + (range 5)) @[0 1 3 6 10]) "accumulate2 1")
+
 (end-suite)