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-- This source is licensed under the Sunset License v1.0
with
Ada.Text_IO,
Packrat.Standard,
Packrat.Utilities;
use
Ada.Text_IO;
procedure Sentence is
Input : String := "i saw a man in the park with a bat";
type Lexer_Labels is (Word, Whitespace);
type Parser_Labels is (S, NP, PP, VP, Det, Noun, Verb, Prep);
package My_Rat is new Packrat.Standard
(Lexer_Labels, Parser_Labels, Character, String);
function Sat_Alpha is new My_Rat.Lexers.Satisfy (Packrat.Utilities.Is_Letter);
function Many_Alpha is new My_Rat.Lexers.Many (Sat_Alpha, 1);
function Word is new My_Rat.Lexers.Stamp (Word, Many_Alpha);
function Sat_Blank is new My_Rat.Lexers.Satisfy (Packrat.Utilities.Is_Whitespace);
function Many_Blank is new My_Rat.Lexers.Many (Sat_Blank, 1);
function Whitespace is new My_Rat.Lexers.Ignore (Whitespace, Many_Blank);
package Scanner is new My_Rat.Lexers.Scan_Once ((Word'Access, Whitespace'Access));
function Is_In is new My_Rat.Lexer_Tokens.Is_Value ("in");
function Is_With is new My_Rat.Lexer_Tokens.Is_Value ("with");
function Sat_In is new My_Rat.Parsers.Satisfy (Is_In);
function Sat_With is new My_Rat.Parsers.Satisfy (Is_With);
function Prep_Choice is new My_Rat.Parsers.Choice ((Sat_In'Access, Sat_With'Access));
function Prep is new My_Rat.Parsers.Stamp (Prep, Prep_Choice);
function Is_Saw is new My_Rat.Lexer_Tokens.Is_Value ("saw");
function Sat_Saw is new My_Rat.Parsers.Satisfy (Is_Saw);
function Verb is new My_Rat.Parsers.Stamp (Verb, Sat_Saw);
function Is_I is new My_Rat.Lexer_Tokens.Is_Value ("i");
function Is_Man is new My_Rat.Lexer_Tokens.Is_Value ("man");
function Is_Park is new My_Rat.Lexer_Tokens.Is_Value ("park");
function Is_Bat is new My_Rat.Lexer_Tokens.Is_Value ("bat");
function Sat_I is new My_Rat.Parsers.Satisfy (Is_I);
function Sat_Man is new My_Rat.Parsers.Satisfy (Is_Man);
function Sat_Park is new My_Rat.Parsers.Satisfy (Is_Park);
function Sat_Bat is new My_Rat.Parsers.Satisfy (Is_Bat);
function Noun_Choice is new My_Rat.Parsers.Choice
((Sat_I'Access, Sat_Man'Access, Sat_Park'Access, Sat_Bat'Access));
function Noun is new My_Rat.Parsers.Stamp (Noun, Noun_Choice);
function Is_A is new My_Rat.Lexer_Tokens.Is_Value ("a");
function Is_The is new My_Rat.Lexer_Tokens.Is_Value ("the");
function Sat_A is new My_Rat.Parsers.Satisfy (Is_A);
function Sat_The is new My_Rat.Parsers.Satisfy (Is_The);
function Det_Choice is new My_Rat.Parsers.Choice ((Sat_A'Access, Sat_The'Access));
function Det is new My_Rat.Parsers.Stamp (Det, Det_Choice);
-- These redirectors are needed to resolve circular references in the instantiations.
package NP_Redir is new My_Rat.Parsers.Redirect;
package S_Redir is new My_Rat.Parsers.Redirect;
function VP_Seq is new My_Rat.Parsers.Sequence ((Verb'Access, NP_Redir.Call'Access));
function VP is new My_Rat.Parsers.Stamp (VP, VP_Seq);
function PP_Seq is new My_Rat.Parsers.Sequence ((Prep'Access, NP_Redir.Call'Access));
function PP is new My_Rat.Parsers.Stamp (PP, PP_Seq);
function NP_Seq_1 is new My_Rat.Parsers.Sequence ((Det'Access, Noun'Access));
function NP_Seq_2 is new My_Rat.Parsers.Sequence ((NP_Redir.Call'Access, PP'Access));
function NP_Choice is new My_Rat.Parsers.Choice
((Noun'Access, NP_Seq_1'Access, NP_Seq_2'Access));
function NP is new My_Rat.Parsers.Stamp (NP, NP_Choice);
function S_Seq_1 is new My_Rat.Parsers.Sequence ((NP'Access, VP'Access));
function S_Seq_2 is new My_Rat.Parsers.Sequence ((S_Redir.Call'Access, PP'Access));
function S_Choice is new My_Rat.Parsers.Choice ((S_Seq_1'Access, S_Seq_2'Access));
function S is new My_Rat.Parsers.Stamp (S, S_Choice);
package Parser is new My_Rat.Parsers.Parse_Once (S);
Lexed_Tokens : My_Rat.Lexer_Result := Scanner.Scan (Input);
Result_Graph : My_Rat.Parser_Result;
begin
-- Very important!
-- If these aren't set before calling the parser, an exception will be raised.
NP_Redir.Set (NP'Access);
S_Redir.Set (S'Access);
Result_Graph := Parser.Parse (Lexed_Tokens);
Put_Line ("Input:");
Put_Line (Input);
New_Line;
Put_Line ("Lexer token output:");
for T of Lexed_Tokens loop
Put (My_Rat.Lexer_Tokens.Debug_String (T));
end loop;
New_Line;
Put_Line ("Parser graph output:");
Put_Line (My_Rat.Parse_Graphs.Debug_String (Result_Graph));
New_Line;
Put_Line ("Root tokens:");
for T of Result_Graph.Root_Elements loop
Put (My_Rat.Parser_Tokens.Debug_String (T));
end loop;
end Sentence;
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