1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
|
#!/usr/bin/perl
# Copyright 2022 Jeffrey Kegler
# This file is part of Marpa::R2. Marpa::R2 is free software: you can
# redistribute it and/or modify it under the terms of the GNU Lesser
# General Public License as published by the Free Software Foundation,
# either version 3 of the License, or (at your option) any later version.
#
# Marpa::R2 is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser
# General Public License along with Marpa::R2. If not, see
# http://www.gnu.org/licenses/.
# Engine Synopsis
use 5.010001;
use strict;
use warnings;
use Test::More tests => 3;
use lib 'inc';
use Marpa::R2::Test;
## no critic (ErrorHandling::RequireCarping);
# Marpa::R2::Display
# name: Engine Synopsis Unambiguous Parse
use Marpa::R2;
my $grammar = Marpa::R2::Grammar->new(
{ start => 'Expression',
actions => 'My_Actions',
default_action => 'first_arg',
rules => [
{ lhs => 'Expression', rhs => [qw/Term/] },
{ lhs => 'Term', rhs => [qw/Factor/] },
{ lhs => 'Factor', rhs => [qw/Number/] },
{ lhs => 'Term', rhs => [qw/Term Add Term/], action => 'do_add' },
{ lhs => 'Factor',
rhs => [qw/Factor Multiply Factor/],
action => 'do_multiply'
},
],
}
);
$grammar->precompute();
my $recce = Marpa::R2::Recognizer->new( { grammar => $grammar } );
$recce->read( 'Number', 42 );
$recce->read('Multiply');
$recce->read( 'Number', 1 );
$recce->read('Add');
$recce->read( 'Number', 7 );
sub My_Actions::do_add {
my ( undef, $t1, undef, $t2 ) = @_;
return $t1 + $t2;
}
sub My_Actions::do_multiply {
my ( undef, $t1, undef, $t2 ) = @_;
return $t1 * $t2;
}
sub My_Actions::first_arg { shift; return shift; }
my $value_ref = $recce->value;
my $value = $value_ref ? ${$value_ref} : 'No Parse';
# Marpa::R2::Display::End
# Ambiguous, Array Form Rules
# Marpa::R2::Display
# name: Engine Synopsis Ambiguous Parse
use Marpa::R2;
my $ambiguous_grammar = Marpa::R2::Grammar->new(
{ start => 'E',
actions => 'My_Actions',
rules => [
[ 'E', [qw/E Add E/], 'do_add' ],
[ 'E', [qw/E Multiply E/], 'do_multiply' ],
[ 'E', [qw/Number/], ],
],
default_action => 'first_arg',
}
);
$ambiguous_grammar->precompute();
my $ambiguous_recce =
Marpa::R2::Recognizer->new( { grammar => $ambiguous_grammar } );
$ambiguous_recce->read( 'Number', 42 );
$ambiguous_recce->read('Multiply');
$ambiguous_recce->read( 'Number', 1 );
$ambiguous_recce->read('Add');
$ambiguous_recce->read( 'Number', 7 );
my @values = ();
while ( defined( my $ambiguous_value_ref = $ambiguous_recce->value() ) ) {
push @values, ${$ambiguous_value_ref};
}
# Marpa::R2::Display::End
Test::More::is( $value, 49, 'Unambiguous Value' );
Test::More::is_deeply( [ sort @values ], [ 336, 49 ], 'Ambiguous Values' );
# An example of "Ruby Slippers" lexing, using
# the unambiguous grammar.
sub fix_things {
my ($recce, $tokens, $token_ix) = @_;
die qq{Don't know how to fix things at $token_ix};
}
# Marpa::R2::Display
# name: Engine Synopsis Interactive Parse
$recce = Marpa::R2::Recognizer->new( { grammar => $grammar } );
my @tokens = (
[ 'Number', 42 ],
['Multiply'], [ 'Number', 1 ],
['Add'], [ 'Number', 7 ],
);
TOKEN: for ( my $token_ix = 0; $token_ix <= $#tokens; $token_ix++ ) {
defined $recce->read( @{ $tokens[$token_ix] } )
or fix_things( $recce, $token_ix, \@tokens )
or die q{Don't know how to fix things};
}
# Marpa::R2::Display::End
$value_ref = $recce->value;
$value = $value_ref ? ${$value_ref} : 'No Parse';
Test::More::is( $value, 49, 'Interactive Value' );
1; # In case used as "do" file
# Local Variables:
# mode: cperl
# cperl-indent-level: 4
# fill-column: 100
# End:
# vim: expandtab shiftwidth=4:
|
