You can reduce the complexity in the TOP reduction method by preparing ASTs in the reduction methods of the previous rules (read that backwards to get the actual order of execution): 
class H::Actions {
    # construct a hash from a list of pairs
    method TOP($/)  {
        make  %($<pairs>.ast);
    }

    # construct a list of Str => Match pairs
    method pairs($/){ make @($<pair>».ast) }

    # construct a Str => Match pair
    method pair($/) { make ~$<key> => $<mash> };
}

[download]

You could also try to stuff all the complexity in method TOP, and use meta operators and parallel dispatch to replace the loop, but I think it will be harder to write, read and debug. Still here's an untested suggestion: 

my @a = @($/<pairs><pair>)

make %( @a».<key>».Str Z=> @a».<mash> )

[download]

since the hash indexing with .<key> is just a method call, it can be applied to all items in an array or list with <c>».</code> parallel dispatch (or >>. if you are an ASCII fan).

Z=> is the Zip meta operator with the => pair constructor. It takes an item from each list, constructs a pair from them, then takes the second item from each list etc.

Perl 6 - links to (nearly) everything that is Perl 6.

In reply to Re: P6: grammar: create a hash instead of array? by moritz
in thread P6: grammar: create a hash instead of array? by rir

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.