From f10443f5b1a073a71830b0445a9d481373386c84 Mon Sep 17 00:00:00 2001
From: Matthew Hammer <matthew@dfinity.org>
Date: Tue, 27 Apr 2021 14:11:45 -0600
Subject: [PATCH 1/3] Trie tries to avoid asserting false.

---
 src/Trie.mo | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/Trie.mo b/src/Trie.mo
index a3e19ae6..01b2a9ae 100644
--- a/src/Trie.mo
+++ b/src/Trie.mo
@@ -95,6 +95,16 @@ public type Key<K> = {
 
 type List<T> = List.List<T>;
 
+public func hashBit(bits: Hash.Hash, bitPos: Nat) : Bool {
+  if(bitPos <= Hash.length) {
+    Hash.bit(bits, bitPos)
+  } else {
+    // rather than assert false (as with Hash.bit),
+    // we simply give zero for all higher bits.
+    0
+  }
+};
+
 /// Equality function for two `Key<K>`s, in terms of equality of `K`'s.
 public func equalKey<K>(keq:(K,K) -> Bool) : ((Key<K>,Key<K>) -> Bool) {
   func (key1:Key<K>, key2:Key<K>) : Bool {
@@ -293,7 +303,7 @@ public func replace<K,V>(t : Trie<K,V>, k:Key<K>, k_eq:(K,K)->Bool, v:?V) : (Tri
             (leaf<K,V>(kvs, bitpos), null)
           };
      case (#branch(b)) label profile_trie_replace_rec_branch : (Trie<K,V>, ?V) {
-            let bit = Hash.bit(k.hash, bitpos);
+            let bit = hashBit(k.hash, bitpos);
             // rebuild either the left or right path with the (k,v) pair
             if (not bit) {
               let (l, v_) = rec(b.left, bitpos+1);
@@ -336,7 +346,7 @@ public func find<K,V>(t : Trie<K,V>, k:Key<K>, k_eq:(K,K) -> Bool) : ?V = label
               { AssocList.find<Key<K>,V>(l.keyvals, k, key_eq) }
             };
        case (#branch(b)) {
-            let bit = Hash.bit(k.hash, bitpos);
+            let bit = hashBit(k.hash, bitpos);
             if (not bit) {
                 label profile_trie_find_branch_left : (?V)
                 { rec(b.left, bitpos+1) }
@@ -360,7 +370,7 @@ func splitAssocList<K,V>(al:AssocList<Key<K>,V>, bitpos:Nat)
    List.partition<(Key<K>,V)>(
      al,
      func ((k : Key<K>, v : V)) : Bool {
-       not Hash.bit(k.hash, bitpos)
+       not hashBit(k.hash, bitpos)
      }
    )
  };
@@ -375,7 +385,7 @@ func splitList<K,V>(l:AssocList<Key<K>,V>, bitpos:Nat)
      case null { (0, null, 0, null) };
      case (?((k,v),t)) {
             let (cl, l, cr, r) = rec(t) ;
-            if (not Hash.bit(k.hash, bitpos)){
+            if (not hashBit(k.hash, bitpos)){
               (cl + 1, ?((k,v),l), cr, r)
             } else {
               (cl, l, cr + 1, ?((k,v),r))

From 9934584172f320dc374df34faa7b3813ebf90f28 Mon Sep 17 00:00:00 2001
From: Matthew Hammer <matthew@dfinity.org>
Date: Tue, 27 Apr 2021 14:21:14 -0600
Subject: [PATCH 2/3] bool type

---
 src/Trie.mo | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Trie.mo b/src/Trie.mo
index 01b2a9ae..f7fc7881 100644
--- a/src/Trie.mo
+++ b/src/Trie.mo
@@ -1,4 +1,4 @@
-/// Functional maps
+s/// Functional maps
 ///
 /// Functional maps (and sets) whose representation is "canonical", and
 /// independent of their operation history (unlike other popular search trees).
@@ -101,7 +101,7 @@ public func hashBit(bits: Hash.Hash, bitPos: Nat) : Bool {
   } else {
     // rather than assert false (as with Hash.bit),
     // we simply give zero for all higher bits.
-    0
+    false
   }
 };
 

From a3be754559aaecf86fc0d13f98f2382914bdba62 Mon Sep 17 00:00:00 2001
From: Matthew Hammer <matthew@dfinity.org>
Date: Tue, 27 Apr 2021 14:44:08 -0600
Subject: [PATCH 3/3] thanks Yan

---
 src/Trie.mo | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Trie.mo b/src/Trie.mo
index f7fc7881..791b72d4 100644
--- a/src/Trie.mo
+++ b/src/Trie.mo
@@ -1,4 +1,4 @@
-s/// Functional maps
+/// Functional maps
 ///
 /// Functional maps (and sets) whose representation is "canonical", and
 /// independent of their operation history (unlike other popular search trees).