Initial data commit

Task/Combinations/SparForte/combinations.sparforte

@@ -0,0 +1,81 @@
+#!/usr/local/bin/spar
+pragma annotate( summary, "combinations" )
+       @( description, "Given non-negative integers m and n, generate all size m" )
+       @( description, "combinations of the integers from 0 to n-1 in sorted" )
+       @( description, "order (each combination is sorted and the entire table" )
+       @( description, "is sorted" )
+       @( see_also, "http://rosettacode.org/wiki/Combinations" )
+       @( author, "Ken O. Burtch" );
+
+pragma restriction( no_external_commands );
+
+procedure combinations is
+  number_of_items : constant natural := 3;
+  max_item_value  : constant natural := 5;
+
+  -- get_first_combination
+  -- return the first combination (e.g. 0,1,2 for 3 items)
+
+  function get_first_combination return string is
+    c : string;
+  begin
+    for i in 1..number_of_items loop
+      c := @ & strings.image( natural( i-1 ) );
+    end loop;
+    return c;
+  end get_first_combination;
+
+  -- get_last_combination
+  -- return the highest value (e.g. 4,4,4 for 3 items
+  -- with a maximum value of 5).
+
+  function get_last_combination return string is
+    c : string;
+  begin
+    for i in 1..number_of_items loop
+      c := @ & strings.image( max_item_value-1 );
+    end loop;
+    return c;
+  end get_last_combination;
+
+  combination : string := get_first_combination;
+  last_combination : constant string := get_last_combination;
+
+  item : natural; -- a number from the combination
+  bad : boolean; -- true if we know a value is too big
+  s : string;    -- a temp string for deleting leading space
+
+begin
+  put_line( combination );
+  while combination /= last_combination loop
+
+    -- the combination is 3 numbers with leading spaces
+    -- so the field positions start at 2 (1 is a null string)
+
+    for i in reverse 1..number_of_items loop
+        item := numerics.value( strings.field( combination, i+1, ' ') );
+        if item < max_item_value-1 then
+           item := @+1;
+           s := strings.image( item );
+           s := strings.delete( s, 1, 1 );
+           strings.replace( combination, i+1, s, ' ' );
+           bad := false;
+           for j in i+1..number_of_items loop
+              item := numerics.value( strings.field( combination, j, ' ') );
+              if item < max_item_value-1 then
+                 item := @+1;
+                 s := strings.image( item );
+                 s := strings.delete( s, 1, 1 );
+                 strings.replace( combination, j+1, s, ' ' );
+              else
+                 bad;
+                  end if;
+           end loop;
+           exit;
+        end if;
+    end loop;
+        if not bad then
+           put_line( combination );
+    end if;
+  end loop;
+end combinations;