Add scanPairs for non-hash tables

scanPairs(x, f) is the same as scan(pairs x, f)

M2/Macaulay2/d/actors3.d

@@ -2363,6 +2363,20 @@ scan(e:Expr):Expr := (
      else WrongNumArgs(2));
 setupfun("scan",scan);
 
+-- # typical value: scanPairs, Thing, Function, Nothing
+scanPairs(e:Expr):Expr := (
+    when e
+    is a:Sequence do (
+	if length(a) == 2 then (
+	    when a.0
+	    is o:HashTable do (
+		if o.Mutable then WrongArgImmutableHashTable(1)
+		else scanpairs(a.1, o))
+	    else scan(pairs(a.0), a.1))
+	else WrongNumArgs(2))
+    else WrongNumArgs(2));
+setupfun("scanPairs", scanPairs);
+
 nextPrime(e:Expr):Expr := (
      when e
      is x:ZZcell do toExpr(nextPrime(x.v - oneZZ))

M2/Macaulay2/d/evaluate.d

@@ -1710,7 +1710,7 @@ setup(LeftArrowS,assigntofun);
 idfun(e:Expr):Expr := e;
 setupfun("identity",idfun);
 -- # typical value: scanPairs, HashTable, Function, Nothing
-scanpairs(f:Expr,obj:HashTable):Expr := (	-- obj is not Mutable
+export scanpairs(f:Expr,obj:HashTable):Expr := (	-- obj is not Mutable
      foreach bucket in obj.table do (
 	  p := bucket;
 	  while true do (
@@ -1720,18 +1720,6 @@ scanpairs(f:Expr,obj:HashTable):Expr := (	-- obj is not Mutable
 	       p = p.next;
 	       ));
      nullE);
-scanpairsfun(e:Expr):Expr := (
-     when      e is a:Sequence do
-     if        length(a) == 2
-     then when a.0 is o:HashTable 
-     do
-     if	       o.Mutable
-     then      WrongArgImmutableHashTable()
-     else      scanpairs(a.1,o)
-     else      WrongArgHashTable(1)
-     else      WrongNumArgs(2)
-     else      WrongNumArgs(2));
-setupfun("scanPairs",scanpairsfun);
 
 mpre():Expr := buildErrorPacket("applyPairs: expected function to return null, a sequence of length 2, or an option x=>y");
 -- # typical value: applyPairs, HashTable, Function, HashTable

M2/Macaulay2/packages/Macaulay2Doc/doc_tables.m2

@@ -388,12 +388,14 @@ doc ///
  Key
   scanPairs
   (scanPairs, HashTable, Function)
+  (scanPairs, Thing, Function)
  Headline
   apply a function to the pairs in a hash table
  Usage
   scanPairs(t, f)
  Inputs
-  t:HashTable
+  t:{HashTable, BasicList, Dictionary}
+    or any instance of a class with an @TO iterator@ method installed
   f:Function
  Description
   Text
@@ -404,7 +406,12 @@ doc ///
   Example
    t = hashTable {{1,8},{2,20},{3,4},{4,20}}
    scanPairs(t, (k,v) -> print (k+v))
-   scanPairs(t, (k,v) -> if v==20 then print k)   
+   scanPairs(t, (k,v) -> if v==20 then print k)
+  Text
+   If @CODE "t"@ is not a hash table, then @M2CODE "scan(pairs t, f)"@ is
+   called.
+  Example
+   scanPairs({4, 5, 6}, print)
  Caveat
   This function requires an immutable hash table.  To scan the pairs in
   a mutable hash table, use {\tt scan(pairs t, f)}.

M2/Macaulay2/tests/normal/iterators.m2

@@ -56,3 +56,6 @@ assert Equation(join([1, 2, 3], iterator {4, 5, 6}), [1, 2, 3, 4, 5, 6])
 assert Equation(toList pairs "foo", {(0, "f"), (1, "o"), (2, "o")})
 assert Equation(toList applyPairs("foo", (i, c) -> (c, i + 1)),
     {("f", 1), ("o", 2), ("o", 3)})
+x = 0
+scanPairs("foo", (i, c) -> x += i + first ascii c)
+assert Equation(x, 0 + 102 + 1 + 111 + 2 + 111)