Question

我有一个相当大的Marpa语法（用于解析XPath），我遇到了令牌化的问题。我在下面创建了一个最小的破解示例：

use strict;
use warnings;
use Marpa::R2;

my $grammar = Marpa::R2::Scanless::G->new(
    {
        source => \(<<'END_OF_SOURCE'),
            :default ::= action => ::array
            :start ::= Start

            Start  ::= Child DoubleColon Token

            DoubleColon ~ '::'
            Child ~ 'child'
            Token ~
                word
                | word ':' word
            word ~ [\w]+

END_OF_SOURCE
    }
);
my $reader = Marpa::R2::Scanless::R->new(
    {
        grammar => $grammar,
        trace_terminals => 1,
    }
);

my $input = 'child::book';
$reader->read(\$input);

此脚本打印以下内容：

Registering character U+0063 as symbol 10: [[\w]]
Registering character U+0063 as symbol 3: [[c]]
Registering character U+0068 as symbol 10: [[\w]]
Registering character U+0068 as symbol 4: [[h]]
Registering character U+0069 as symbol 10: [[\w]]
Registering character U+0069 as symbol 5: [[i]]
Registering character U+006c as symbol 10: [[\w]]
Registering character U+006c as symbol 6: [[l]]
Registering character U+0064 as symbol 10: [[\w]]
Registering character U+0064 as symbol 7: [[d]]
Registering character U+003a as symbol 1: [[\:]]
Rejected lexeme @0-5: Token; value="child"
Accepted lexeme @0-5: Child; value="child"
Registering character U+0062 as symbol 10: [[\w]]
Error in SLIF G1 read: No lexeme found at position 6
* String before error: child::
* The error  was at line 1, column 8, and at character 0x0062 'b', ...
* here: book

我希望将输入标记为[Child] [DoubleColon] [word]。如终端跟踪显示，只读取和处理一个冒号字符。它似乎试图将字符串的开头标记为[word] [':'] [word]并且在中途失败。如果删除语法的第10行（| word ':' word），将不再抛出该错误。

我尝试为DoubleColon（:lexeme ~ <DoubleColon> priority > 1）创建优先级，但这不起作用。有人能告诉我该怎么做才能使这个语法正确解析输入字符串吗？它仍然需要能够解析child::ns:book等。

Answer 1

这似乎是Marpa :: R2当前版本2.058中的一个错误。我很抱歉，感谢您仔细阅读问题。

我有一个修复程序，它通过了测试套件，我很快就会发布一个新版本。

使用Marpa进行不正确的标记化

1 个答案: