Index: src/natools-smaz-tools.adb
==================================================================
--- src/natools-smaz-tools.adb
+++ src/natools-smaz-tools.adb
@@ -346,6 +346,53 @@
             Values => Values,
             Hash => Dummy_Hash'Access);
       end;
    end To_Dictionary;
 
+
+
+   -------------------
+   -- Word Counting --
+   -------------------
+
+   procedure Add_Substrings
+     (Counter : in out Word_Counter;
+      Phrase : in String;
+      Min_Size : in Positive;
+      Max_Size : in Positive) is
+   begin
+      for First in Phrase'First .. Phrase'Last - Min_Size + 1 loop
+         for Last in First + Min_Size - 1
+           .. Natural'Min (First + Max_Size - 1, Phrase'Last)
+         loop
+            Add_Word (Counter, Phrase (First .. Last));
+         end loop;
+      end loop;
+   end Add_Substrings;
+
+
+   procedure Add_Word
+     (Counter : in out Word_Counter;
+      Word : in String;
+      Count : in String_Count := 1)
+   is
+      procedure Update
+        (Key : in String; Element : in out String_Count);
+
+      procedure Update
+        (Key : in String; Element : in out String_Count)
+      is
+         pragma Unreferenced (Key);
+      begin
+         Element := Element + Count;
+      end Update;
+
+      Cursor : constant Word_Maps.Cursor := Word_Maps.Find (Counter.Map, Word);
+   begin
+      if Word_Maps.Has_Element (Cursor) then
+         Word_Maps.Update_Element (Counter.Map, Cursor, Update'Access);
+      else
+         Word_Maps.Insert (Counter.Map, Word, Count);
+      end if;
+   end Add_Word;
+
 end Natools.Smaz.Tools;

Index: src/natools-smaz-tools.ads
==================================================================
--- src/natools-smaz-tools.ads
+++ src/natools-smaz-tools.ads
@@ -22,10 +22,12 @@
 ------------------------------------------------------------------------------
 
 with Ada.Containers.Indefinite_Doubly_Linked_Lists;
 with Natools.S_Expressions;
 
+private with Ada.Containers.Indefinite_Ordered_Maps;
+
 package Natools.Smaz.Tools is
    pragma Preelaborate;
 
    package String_Lists is new Ada.Containers.Indefinite_Doubly_Linked_Lists
      (String);
@@ -63,7 +65,36 @@
 
    List_For_Linear_Search : String_Lists.List;
    function Linear_Search (Value : String) return Natural;
       --  Function and data source for inefficient but dynamic function
       --  that can be used with Dictionary.Hash.
+
+   type String_Count is range 0 .. 2 ** 31 - 1;
+      --  Type for a number of substring occurrences
+
+   type Word_Counter is private;
+      --  Accumulate frequency/occurrence counts for a set of strings
+
+   procedure Add_Word
+     (Counter : in out Word_Counter;
+      Word : in String;
+      Count : in String_Count := 1);
+      --  Include Count number of occurrences of Word in Counter
+
+   procedure Add_Substrings
+     (Counter : in out Word_Counter;
+      Phrase : in String;
+      Min_Size : in Positive;
+      Max_Size : in Positive);
+      --  Include all the substrings of Phrase whose lengths are
+      --  between Min_Size and Max_Size.
+
+private
+
+   package Word_Maps is new Ada.Containers.Indefinite_Ordered_Maps
+     (String, String_Count);
+
+   type Word_Counter is record
+      Map : Word_Maps.Map;
+   end record;
 
 end Natools.Smaz.Tools;