Re: Text parsing package

[Syntax Issues <syntax.issues@gmail.com>]

Thanks for posting the techniques Dmitry. I am going to try
implementing as many as I can -- I am still a fairly new programmer,
and I still have a lot to learn.
Right now it uses text_io and strings.unbounded.text_io (this is
probably bad :/) and only works with files. I tried to make it as
simple as possible with exception checking -- global booleans are set
and checked by the running program.
-- Spec
with
	Ada.Exceptions,
	Ada.Text_Io,
	Ada.Strings.Unbounded.Text_Io,
	Ada.Strings.Unbounded;
use
	Ada.Exceptions,
	Ada.Text_Io,
	Ada.Strings.Unbounded.Text_Io,
	Ada.Strings.Unbounded;
package Parsing
	is
	---------------
	-- Constants --
	---------------
		DEBUGGING_ON                  : constant Boolean          := true;
		EXCEPTION_PARSE_NOTHING       : constant String           :=
"Attempted to parse passed the end-of-file.";
		EXCEPTION_PARSE_UNOPENED_FILE : constant String           :=
"Attempted to parse an unopened file.";
		EXCEPTION_PARSE_NON_NUMBER    : constant String           := "Failed
to parse a number.";
		NULL_STRING_FIXED             : constant String           := "";
		NULL_STRING_UNBOUNDED         : constant Unbounded_String :=
To_Unbounded_String(NULL_STRING_FIXED);
	--------------
	-- Packages --
	--------------
		package Io_Integer
			is new Ada.Text_Io.Integer_Io(Integer);
		package Io_Float
			is new Ada.Text_Io.Float_Io(Float);
	---------------
	-- Variables --
	---------------
		Error_On_Recent_Operation  : Boolean          := false;
		Error_Occured_Parsing_File : Boolean          := false;
		Line                       : Unbounded_String :=
NULL_STRING_UNBOUNDED;
		File                       : File_Type;
	-----------------
	-- Subprograms --
	-----------------
		procedure Open
			(Name : in String);
			pragma Inline(Open);
		procedure Close;
			pragma Inline(Close);
		function Next_Unbounded_String
			return Unbounded_String;
		function Next_String
			return String;
			pragma Inline(Next_String);
		function Next_Integer
			return Integer;
		function Next_Float
			return Float;
	end Parsing;
--- Body
package body Parsing
	is
	--
	-- Open_File
	--
	procedure Open
		(Name : in String)
		is
		begin
			Ada.Text_Io.Open(File, In_File, Name);
			if not End_Of_File(File) then
				Line := Get_Line(File);
			end if;
		end Open;
	--
	-- Close_File
	--
	procedure Close
		is
		begin
			if Is_Open(File) then
				Ada.Text_Io.Close(File);
				Error_Occured_Parsing_File := false;
			end if;
		end Close;
	--
	-- Next_Unbounded_String
	--
	function Next_Unbounded_String
		return Unbounded_String
		is
		Result : Unbounded_String := NULL_UNBOUNDED_STRING;
		begin
			Error_On_Recent_Operation := false;
			Trim(Line, Ada.Strings.Both);
			if not Is_Open(File) then
				if DEBUGGING_ON then
					Put_Line(EXCEPTION_PARSE_UNOPENED_FILE);
				end if;
				Error_Occured_Parsing_File := true;
				Error_On_Recent_Operation  := true;
				return Result;
			end if;
			loop
				if Length(Line) /= 0 then
					for I in 1..Length(Line) loop
						if Element(Line, I) = ' ' or I = Length(Line) then
							Result := To_Unbounded_String(Slice(Line, 1, I));
							Delete(Line, 1, I);
							return Result;
						end if;
					end loop;
				else
					if End_Of_File(File) then
						if DEBUGGING_ON then
							Put_Line(EXCEPTION_PARSE_NOTHING);
						end if;
						Error_Occured_Parsing_File := true;
						Error_On_Recent_Operation  := true;
						return Result;
					end if;
					Line := Trim(Get_Line(File), Ada.Strings.Both);
				end if;
			end loop;
		end Next_Unbounded_String;
	--
	-- Next_String
	--
	function Next_String
		return String
		is
		begin
			return To_String(Next_Unbounded_String);
		end Next_String;
	--
	-- Next_Integer
	--
	function Next_Integer
		return Integer
		is
		Last   : Positive;
		Result : Integer := 0;
		begin
			Io_Integer.Get(To_String(Next_Unbounded_String), Result, Last);
			return Result;
			exception
				when Data_Error | Constraint_Error =>
					if DEBUGGING_ON then
						Put_Line(EXCEPTION_PARSE_NON_NUMBER);
					end if;
					Error_Occured_Parsing_File := true;
					Error_On_Recent_Operation  := true;
					return Result;
		end Next_Integer;
	--
	-- Next_Float
	--
	function Next_Float
		return Float
		is
		Last   : Positive;
		Result : Float := 0.0;
		begin
			Io_Float.Get(To_String(Next_Unbounded_String), Result, Last);
			return Result;
			exception
				when Data_Error | Constraint_Error =>
					if DEBUGGING_ON then
						Put_Line(EXCEPTION_PARSE_NON_NUMBER);
					end if;
					Error_Occured_Parsing_File := true;
					Error_On_Recent_Operation  := true;
					return Result;
		end Next_Float;
	end Parsing;