From 1110267c9dbed3bdbfa6dc206d125fabd2deed44 Mon Sep 17 00:00:00 2001
From: Calvin Rose <Calvin@Rose-Family-iMac-5.local>
Date: Sun, 1 Apr 2018 15:08:51 -0400
Subject: [PATCH] Update maxtriangle example, extend map function, and add
 extremes functions (max, min, order-max, order-min, extreme)

---
 examples/maxtriangle.dst | 32 +++++++------------------------
 src/compiler/boot.dst    | 41 ++++++++++++++++++++++++++++++++++------
 2 files changed, 42 insertions(+), 31 deletions(-)

diff --git a/examples/maxtriangle.dst b/examples/maxtriangle.dst
index ee895f5e..6cf24387 100644
--- a/examples/maxtriangle.dst
+++ b/examples/maxtriangle.dst
@@ -1,36 +1,18 @@
 # Find the maximum path from the top (root)
 # of the triangle to the leaves of the triangle.
   
-(defn vmap2 [f m1 m2] 
- (def len (length m1))
- (def arr @[])
- (for [i 0 len] (array-push arr (f (get m1 i) (get m2 i))))
- arr)
-
-(defn reduce [s f c]
- (var res s)
- (for [i 0 (length c)]
-  (:= res (f res (get c i))))
- res)
-
-(defn max1 [l r] (if (< l r) r l))
-    
 (defn myfold [xs ys]
  (def xs1 (tuple-prepend xs 0))
  (def xs2 (tuple-append xs 0))
- (def m1 (vmap2 + xs1 ys))
- (def m2 (vmap2 + xs2 ys))
- (vmap2 max1 m1 m2))
-
-(defn max [a]
- (var m (get a 0))
- (for [i 0 (length a)]
-  (if (< m (get a i))
-   (:= m (get a i))))
- m)
+ (def m1 (map + xs1 ys))
+ (def m2 (map + xs2 ys))
+ (map max m1 m2))
 
 (defn maxpath [t]
- (max (reduce () myfold t)))
+ (extreme > (reduce myfold () t)))
+
+# Test it
+# Maximum path is 3 -> 10 -> 3 -> 9 for a total of 25
 
 (def triangle @[
  @[3]
diff --git a/src/compiler/boot.dst b/src/compiler/boot.dst
index 2553d426..0fcbcc6a 100644
--- a/src/compiler/boot.dst
+++ b/src/compiler/boot.dst
@@ -304,6 +304,23 @@ evaluates to true."
  [f]
  (fn [x] (not (f x))))
 
+(defn extreme
+ "Returns the most extreme value in args based on the orderer order.
+Returns nil if args is empty."
+ [order args]
+ (def len (length args))
+ (when (pos? len)
+  (var ret (get args 0))
+  (for [i 0 len]
+   (def v (get args i))
+   (if (order v ret) (:= ret v)))
+  ret))
+
+(defn max [& args] (extreme > args))
+(defn min [& args] (extreme < args))
+(defn max-order [& args] (extreme order> args))
+(defn min-order [& args] (extreme order< args))
+
 ###
 ###
 ### Indexed Combinators
@@ -366,13 +383,25 @@ an indexed type (array, tuple) with a function to produce a value."
 (defn map
  "Map a function over every element in an array or tuple and return
 the same type as the input sequence."
- [f ind t]
+ [f & inds]
  (def res @[])
- (for [i 0 (length ind)]
-  (array-push res (f (get ind i))))
- (if (= :tuple (type (or t ind)))
-  (apply1 tuple res)
-  res))
+ (def ninds (length inds))
+ (if (= 0 ninds) (error "expected at least 1 indexed collection."))
+ (var limit (length (get inds 0)))
+ (for [i 0 ninds]
+  (def l (length (get inds i)))
+  (if (< l limit) (:= limit l)))
+ (def [i1 i2 i3 i4] inds)
+ (switch ninds
+  1 (for [i 0 limit] (array-push res (f (get i1 i))))
+  2 (for [i 0 limit] (array-push res (f (get i1 i) (get i2 i))))
+  3 (for [i 0 limit] (array-push res (f (get i1 i) (get i2 i) (get i3 i))))
+  4 (for [i 0 limit] (array-push res (f (get i1 i) (get i2 i) (get i3 i) (get i4 i))))
+  (for [i 0 limit] 
+   (def args @[])
+   (for [j 0 ninds] (array-push args (get (get inds j) i)))
+   (array-push res (apply1 f args))))
+ res)
 
 (defn mapcat
  "Map a function over every element in an array or tuple and