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
|
use v5.10;
use warnings;
use List::Util qw< reduce >;
my $calculator = do{
use Regexp::Grammars;
qr{
\A
<Answer>
(*COMMIT) # <-- Remove this to see the error messages get less accurate
(?:
\Z
|
<warning: (?{ "Extra junk after expression at index $INDEX: '$CONTEXT'" })>
<warning: Expected end of input>
<error:>
)
<rule: Answer>
<[_Operand=Mult]>+ % <[_Op=(\+|\-)]>
(?{ $MATCH = shift @{$MATCH{_Operand}};
for my $term (@{$MATCH{_Operand}}) {
my $op = shift @{$MATCH{_Op}};
if ($op eq '+') { $MATCH += $term; }
else { $MATCH -= $term; }
}
})
|
<error: Expected valid arithmetic expression>
<rule: Mult>
(?:
<[_Operand=Pow]>+ % <[_Op=(\*|/|%)]>
(?{ $MATCH = reduce { eval($a . shift(@{$MATCH{_Op}}) . $b) }
@{$MATCH{_Operand}};
})
)
<rule: Pow>
(?:
<[_Operand=Term]>+ % <_Op=(\^)>
(?{ $MATCH = reduce { $b ** $a } reverse @{$MATCH{_Operand}}; })
)
<rule: Term>
(?:
<MATCH=Literal>
| \( <MATCH=Answer> \)
)
<token: Literal>
(?:
<MATCH=( [+-]? \d++ (?: \. \d++ )?+ )>
|
<error:>
)
}xms
};
#open my $fh, '>', "source_$$";
#say $calculator; die;
while (my $input = <>) {
if ($input =~ $calculator) {
say '--> ', $/{Answer};
}
say {*STDERR} $_ for @!;
}
|
