START: A | B;
A: C | D;
B: C | D;
C: T1 | T2;
D: T3 | T4;
T1: 't1';
T2: 't2';
T3: 't3';
T4: 't4';

S: NP VP | NPA VP;
NPA: D N | NP PP;
NP: D N | NP PP | NPA;
VP: V NP | VP PP;
PP: P NP;
D: "the" | "a";
P: "in" | "with";
V: "saw";
N: "saw" | "girl" | "boy" | "park" | "telescope";

%{
  int yylex();
  void yyerror(const char* msg);
%}

%error-verbose
%glr-parser

%token WORD_A "a"
%token WORD_BOY "boy"
%token WORD_GIRL "girl"
%token WORD_IN "in"
%token WORD_LIKED "liked"
%token WORD_PARK "park"
%token WORD_SAW "saw"
%token WORD_TELESCOPE "telescope"
%token WORD_THE "the"
%token WORD_WITH "with"

%%
S  : NP VP      {puts("S: NP VP");}     %dprec 1
   | NPA VP     {puts("S: NPA VP");}    %dprec 2
   ;
NPA: D N        {puts("NPA: D N");}     %dprec 3
   | NP PP      {puts("NPA: NP PP");}   %dprec 4
   ;
NP : D N        {puts("NP: D N");}      %dprec 6
   | NP PP      {puts("NP: NP PP");}    %dprec 7
   | NPA        {puts("NP: NPA");}      %dprec 10
   ;
VP : V NP       {puts("VP: V NP ");}    %dprec 11
   | VP PP      {puts("VP: VP PP");}    %dprec 12
   ;
PP : P NP       {puts("PP: P NP");}     %dprec 14
   ;
D  : "the"      {puts("D: the");}       %dprec 15
   | "a"        {puts("D: a");}         %dprec 16
   ;
P  : "in"       {puts("P: in");}        %dprec 17
   | "with"     {puts("P: with");}      %dprec 18
   ;
V  : "liked"    {puts("V: liked");}     %dprec 19
   | "saw"      {puts("V: saw");}       %dprec 20
   ;
N  : "girl"     {puts("N: girl");}      %dprec 21
   | "boy"      {puts("N: boy");}       %dprec 22
   | "park"     {puts("N: park");}      %dprec 23
   | "saw"      {puts("N: saw");}       %dprec 24
   | "telescope"{puts("N: telescope");} %dprec 25
   ;
%%

int main(int argc, char** argv) {
  printf("yyparse returned %dn", yyparse());
  return 0;
}

$ make ambig2
bison30 -v -d -o ambig2.c ambig2.y
ambig2.y: warning: 6 shift/reduce conflicts [-Wconflicts-sr]
ambig2.y: warning: 10 reduce/reduce conflicts [-Wconflicts-rr]
gcc-4.8 -ggdb -Wall -D_POSIX_C_SOURCE=200809L -std=c99 -c -o ambig2.o ambig2.c
gcc-4.8   ambig2.o   -o ambig2
rm ambig2.o ambig2.c

$ ./ambig2 <<<"a boy saw a girl"
D: a
N: boy
NPA: D N
V: saw
D: a
N: girl
NPA: D N
NP: NPA
VP: V NP
S: NPA VP
yyparse returned 0

$ ./ambig2 <<<"a saw saw the saw in a saw"
D: a
N: saw
NPA: D N
V: saw
D: the
N: saw
NPA: D N
NP: NPA
VP: V NP
P: in
D: a
N: saw
NPA: D N
NP: NPA
PP: P NP
VP: VP PP
S: NPA VP
yyparse returned 0

%%
%%main
#skip "s+"
#skip "[u000du000a]+"
#token 'the' "the"
#token 'a' "a"
#token 'in' "in"
#token 'with' "with"
#token 'saw' "saw"
#token 'girl' "girl"
#token 'boy' "boy"
#token 'park' "park"
#token 'telescope' "telescope"
%%

S = NP VP ;
S = NPA VP ;
NPA = D N ;
NPA = NP PP ;
NP = D N ;
NP = NP PP ;
NP = NPA ;
VP = V NP ;
VP = VP PP ;
PP = P NP ;
D = 'the' ;
D = 'a';
P = 'in' ;
P = 'with' ;
V = 'saw' ;
N = 'saw' ;
N = 'girl' ;
N = 'boy' ;
N = 'park' ;
N = 'telescope' ;

a boy saw a girln

C:DMSDomainssimpenglishToolsParserSource>run ..domainparser ++AST ....Lexeraboysawagirl.txt
simpenglish Domain Parser Version 2.5.15
Copyright (C) 1996-2013 Semantic Designs, Inc; All Rights Reserved; SD Confidential
Powered by DMS (R) Software Reengineering Toolkit
24 tree nodes in tree.
3 ambiguity nodes in tree.
(AMBIGUITY<S=11>@simpenglish=31@#1f35140^0{2} Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
 (S@simpenglish=1@#1f350e0^1#1f35140:1 Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
  (AMBIGUITY<NP=12>@simpenglish=31@#1f34ba0^1#1f350e0:1{2} Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   (NP@simpenglish=5@#1f34b80^1#1f34ba0:1 Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   |(D@simpenglish=12@#1f34aa0^2#1f34b80:1#1f34b40:1 Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   | ('a'@simpenglish=22@#1f349c0^1#1f34aa0:1[Keyword:0] Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt)'a'
   |)D#1f34aa0
   |(N@simpenglish=18@#1f34b20^2#1f34b80:2#1f34b40:2 Line 1 Column 3 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   | ('boy'@simpenglish=27@#1f34a80^1#1f34b20:1[Keyword:0] Line 1 Column 3 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt)'boy'
   |)N#1f34b20
   )NP#1f34b80
   (NP@simpenglish=7@#1f34c60^1#1f34ba0:2 Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   |(NPA@simpenglish=3@#1f34b40^2#1f35040:1#1f34c60:1 Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   | (D@simpenglish=12@#1f34aa0^2... [ALREADY PRINTED] ...)
   | (N@simpenglish=18@#1f34b20^2... [ALREADY PRINTED] ...)
   |)NPA#1f34b40
   )NP#1f34c60
  )AMBIGUITY#1f34ba0
  (VP@simpenglish=8@#1f34fc0^1#1f350e0:2 Line 1 Column 7 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   (V@simpenglish=15@#1f34d60^1#1f34fc0:1 Line 1 Column 7 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   |('saw'@simpenglish=25@#1f34b00^2#1f34d60:1#1f34d40:1[Keyword:0] Line 1 Column 7 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt)'saw'
   )V#1f34d60
   (AMBIGUITY<NP=12>@simpenglish=31@#1f34f00^2#1f34f80:2#1f34fc0:2{2} Line 1 Column 11 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   |(NP@simpenglish=5@#1f34e60^1#1f34f00:1 Line 1 Column 11 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   | (D@simpenglish=12@#1f34da0^2#1f34e60:1#1f34de0:1 Line 1 Column 11 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   |  ('a'@simpenglish=22@#1f34ce0^1#1f34da0:1[Keyword:0] Line 1 Column 11 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt)'a'
   | )D#1f34da0
   | (N@simpenglish=17@#1f34dc0^2#1f34e60:2#1f34de0:2 Line 1 Column 13 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   |  ('girl'@simpenglish=26@#1f34d80^1#1f34dc0:1[Keyword:0] Line 1 Column 13 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt)'girl'
   | )N#1f34dc0
   |)NP#1f34e60
   |(NP@simpenglish=7@#1f34f20^1#1f34f00:2 Line 1 Column 11 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   | (NPA@simpenglish=3@#1f34de0^1#1f34f20:1 Line 1 Column 11 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   |  (D@simpenglish=12@#1f34da0^2... [ALREADY PRINTED] ...)
   |  (N@simpenglish=17@#1f34dc0^2... [ALREADY PRINTED] ...)
   | )NPA#1f34de0
   |)NP#1f34f20
   )AMBIGUITY#1f34f00
  )VP#1f34fc0
 )S#1f350e0
 (S@simpenglish=2@#1f35040^1#1f35140:2 Line 1 Column 1 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
  (NPA@simpenglish=3@#1f34b40^2... [ALREADY PRINTED] ...)
  (VP@simpenglish=8@#1f34f80^1#1f35040:2 Line 1 Column 7 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   (V@simpenglish=15@#1f34d40^1#1f34f80:1 Line 1 Column 7 File C:/DMS/Domains/simpenglish/Tools/Lexer/aboysawagirl.txt
   |('saw'@simpenglish=25@#1f34b00^2... [ALREADY PRINTED] ...)
   )V#1f34d40
   (AMBIGUITY<NP=12>@simpenglish=31@#1f34f00^2... [ALREADY PRINTED] ...)
  )VP#1f34f80
 )S#1f35040
)AMBIGUITY#1f35140