Stream merge: Difference between revisions
Ada version
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=={{header|Ada}}==
<lang Ada>with Ada.Text_Io;
with Ada.Command_Line;
with Ada.Containers.Indefinite_Holders;
procedure Stream_Merge is
package String_Holders
is new Ada.Containers.Indefinite_Holders (String);
use Ada.Text_Io, String_Holders;
type Stream_Type is
record
File : File_Type;
Value : Holder;
end record;
subtype Index_Type is Positive range 1 .. Ada.Command_Line.Argument_Count;
Streams : array (Index_Type) of Stream_Type;
procedure Fetch (Stream : in out Stream_Type) is
begin
Stream.Value := (if End_Of_File (Stream.File)
then Empty_Holder
else To_Holder (Get_Line (Stream.File)));
end Fetch;
function Next_Stream return Index_Type is
Index : Index_Type := Index_Type'First;
Value : Holder;
begin
for I in Streams'Range loop
if Value.Is_Empty and not Streams (I).Value.Is_Empty then
Value := Streams (I).Value;
Index := I;
elsif not Streams (I).Value.Is_Empty and then Streams (I).Value.Element < Value.Element then
Value := Streams (I).Value;
Index := I;
end if;
end loop;
if Value.Is_Empty then
raise Program_Error;
end if;
return Index;
end Next_Stream;
function More_Data return Boolean
is (for some Stream of Streams => not Stream.Value.Is_Empty);
begin
if Ada.Command_Line.Argument_Count = 0 then
Put_Line ("Usage: prog <file1> <file2> ...");
Put_Line ("Merge the sorted files file1, file2...");
return;
end if;
for I in Streams'Range loop
Open (Streams (I).File, In_File, Ada.Command_Line.Argument (I));
Fetch (Streams (I));
end loop;
while More_Data loop
declare
Stream : Stream_Type renames Streams (Next_Stream);
begin
Put_Line (Stream.Value.Element);
Fetch (Stream);
end;
end loop;
end Stream_Merge;</lang>
=={{header|ALGOL 68}}==
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