[Boost-users] [boost::spirit] Help! Unexpected Leading spaces got injected into a parse tree node

18 Oct 2009

      I have a question regarding unexpected leading spaces got injected into a parse tree node.

Here is my grammar:

Text = leaf_node_d[+digit_p] >> root_node_d[ch_p('=')] >> leaf_node_d[+digit_p];

If I parse "5=5", as expected no extra leading spaces added to the resulting tree nodes.

If I parse "5=     5" (read:5 followed by = followed by 4 spaces and followed by 5), given my grammar definition of leaf_node_d[+digit_p], I am expecting the parse tree node value should not contain any leading spaces.
Yet, I see that the extra 4 spaces is stored in the corresponding parse tree node as shown below. 

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE parsetree SYSTEM "parsetree.dtd">
<!-- 5=  5 -->
<parsetree version="1.0">
    <parsenode>
        <parsenode>
            <value>5</value>
        </parsenode>
        <parsenode>
            <value is_root="1">=</value>
        </parsenode>
        <parsenode>
==>       <value>     5</value>
        </parsenode>
    </parsenode>
</parsetree>

I am wondering if this is a by design or unexpected behavior. If it is a by design behavior, is there a way to trim leading/trailing spaces.

Thanks!

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[Boost-users] [boost::spirit] Help! Unexpected Leading spaces got injected into a parse tree node

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