in reply to Pugs Apocryphon 1 out; technical questions wanted

I read the first Apocryphon and want to ask some questions that will expose my ignorance of the Perl 6 design process, and the fact that my compiler theory is somewhat rusty:

How does Abstract Syntax Trees (AST) work? Why are they useful? Is it possible to explain these in sentences with words containing two syllables or less?

I am so impressed by the work being done on Pugs. Keep up the good work!

pernod
--
Mischief. Mayhem. Soap.

  • Comment on Re: Pugs Apocryphon 1 out; technical questions wanted

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Re^2: Pugs Apocryphon 1 out; technical questions wanted
by audreyt (Hermit) on Feb 26, 2005 at 18:38 UTC
    Thanks for your words of encouragement. :) You can see a simple AST by running: 
    % perl -MO=Concise -e 'print "Hello, $world!"'
a  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
9     <@> print vK ->a
3        <0> pushmark s ->4
-        <1> ex-stringify sK/1 ->9
-           <0> ex-pushmark s ->4
8           <2> concat[t3] sKS/2 ->9
6              <2> concat[t2] sK/2 ->7
4                 <$> const[PV "Hello, "] s ->5
-                 <1> ex-rv2sv sK/1 ->6
5                    <#> gvsv[*world] s ->6
7              <$> const[PV "!"] s ->8

    [download]
    Compare it with Pugs (using r317 on svn.openfoundry.org, with some indenting): 
    % pugs -c -e 'print "Hello, $world!"'
{ Statements
    [(
        App "&prefix:print"
            [App "&prefix:~"
                [App "&infix:~"
                    [Val (VStr "Hello, ")
                    ,App "&infix:~"
                        [Var "$world"
                        ,Val (VStr "!")
                        ] []
                    ] []
                ] []
            ] []
        ,"<interactive>" (line 1, column 1)
    )]
}

    [download]

    That should give you a pretty good idea of what an AST is. :)

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