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Swapna  
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 More options Oct 3 2011, 3:29 pm
From: Swapna <swapna.ra...@gmail.com>
Date: Mon, 3 Oct 2011 12:29:17 -0700 (PDT)
Local: Mon, Oct 3 2011 3:29 pm
Subject: Help in Defining Access methods for nodes in treetop
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Hi,

I am new to treetop parser. I was looking for an asm parser for which
i have a well defined grammar. I wrote the grammar and the  parser is
able to parse through all the intructions. But I am having issues
while writing methods for these rules. An example code is provided
below.

rule Expression
                 Instruction  / comment
                {
                 def to_array
                        return self.elements.to_array
                 end
                 }
        end

        rule Instruction
                 Unary / Tri / Binary
                        {
                        def to_array
                                return self.elements.map {|e| e.to_array}
                        end
                        }

        end

        rule Unary
                 UnaryInst space?

             def_to_array
                        self.elements[0].to_array  # I get an error here saying
self.elements is nil.  But my parser successfully parses the
instruction. I am unable to call the function beyond this point.
                end
        end

        rule UnaryInst
                UnaryOp sat?
                {
                def to_array()
                                return 1
                        end
                        }
end

Looks like something basic. Thanks in advance for the help.


 
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Swapna  
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 More options Oct 4 2011, 3:56 pm
From: Swapna <swapna.ra...@gmail.com>
Date: Tue, 4 Oct 2011 12:56:31 -0700 (PDT)
Local: Tues, Oct 4 2011 3:56 pm
Subject: Re: Help in Defining Access methods for nodes in treetop
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I tried something similar to this working example

  rule assignment
    identifier '=' number {
      def ast ()
        Operation.new(:assignment, identifier.ast, number.ast)
      end
    }
  end

  rule identifier
    [a-zA-Z_] [a-zA-Z0-9_]* { def ast () Identifier.new(text_value)
end }
  end

What I tried was following

rule Instruction
                 Unary / Tri / Binary
                        {
                        def to_array
                                return self.elements.map {|e| e.to_array}
                        end
                        }

        end

        rule Unary
                 UnaryInst space?
                 {
                        def to_array
                                UnaryInst.to_array   # I am unable to call this function here. I
cann access it through self.elements[0].to_array. how to i access
methods of particular rules directly?
                        end
                }

        end

rule UnaryInst
                UnaryOp space?
                {
                def to_array
                        return 1
                end
                }
        end

even in I access UnaryInst.to_array using self.elements[0].to-array. i
would like to call UnaryOp.to_array in the next step. What i see is an
error : uninitialized constant ASM::UnaryInst1::UnaryOp (NameError)

On Oct 3, 12:29 pm, Swapna <swapna.ra...@gmail.com> wrote:


 
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Clifford Heath  
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 More options Oct 3 2011, 5:39 pm
From: Clifford Heath <clifford.he...@gmail.com>
Date: Tue, 4 Oct 2011 08:39:15 +1100
Local: Mon, Oct 3 2011 5:39 pm
Subject: Re: Help in Defining Access methods for nodes in treetop
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On 04/10/2011, at 6:29 AM, Swapna wrote:

> I am having issues while writing methods for these rules. An example code is provided
> below.

> rule Expression
>             Instruction  / comment
>            {

This block only applies to comment, not to Instruction. Use parentheses around (Instruction/comment) to make it apply to both.

>             def to_array
>                    return self.elements.to_array

You don't need to say "self".
"elements" is already an array. Did you mean "elements.map{|e| e.to_array}"?

>             end
>             }
>    end

>    rule Instruction
>             Unary / Tri / Binary

Use parentheses.

>                    {
>                    def to_array
>                            return self.elements.map {|e| e.to_array}
>                    end
>                    }

>    end

>    rule Unary
>             UnaryInst space?

>             def_to_array
>                    self.elements[0].to_array  # I get an error here saying
> self.elements is nil.  But my parser successfully parses the
> instruction. I am unable to call the function beyond this point.

I don't understand that. elements[1] might be nil, because it's optional, but not elements[0].
Normally you should use the element names (or tags) to access the elements, so instead of saying "elements[0]" you can just say "UnaryInst".

Try these things and report back.

Clifford Heath.


 
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Swapna Raj  
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 More options Oct 4 2011, 9:00 pm
From: Swapna Raj <swapna.ra...@gmail.com>
Date: Tue, 4 Oct 2011 18:00:05 -0700
Local: Tues, Oct 4 2011 9:00 pm
Subject: Re: Help in Defining Access methods for nodes in treetop
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Hi Clifford,

Yes I meant elements.map{|e| e.to_array}

Anyways, those issues are resolved now. UnaryOp was a set of terminals which
I had defines as "abc"/"cde"/"efg"...

The issue got resolved when I changed this to ("abc"/"cde"/"efg"...). Now I
am able to use UnaryOp.to_array. Not sure how this matters, since we are
defining the method inside {..}

Another issue I had was in accessing methods for optional non-terminals.
This failed regardless of if C was in the parsed text or not.

For eG;

Rule B

A C?
{
def to_array
return C.to_array
end

}

end

rule C

D "abd"
{
def to_array
return text_value
end

}

end

But works if I change this to

Rule A

B C
{
def to_array
return C.to_array
end

}

end
rule C

D? "abd"?
{
def to_array
return text_value
end

}

end

I am just noting it here, since it might help some one else who is new to
treetop.

On Mon, Oct 3, 2011 at 2:39 PM, Clifford Heath <clifford.he...@gmail.com>wrote:


 
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Clifford Heath  
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 More options Oct 4 2011, 10:20 pm
From: Clifford Heath <clifford.he...@gmail.com>
Date: Wed, 5 Oct 2011 13:20:46 +1100
Local: Tues, Oct 4 2011 10:20 pm
Subject: Re: Help in Defining Access methods for nodes in treetop
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On 05/10/2011, at 12:00 PM, Swapna Raj wrote:

> Anyways, those issues are resolved now. UnaryOp was a set of terminals which I had defines as "abc"/"cde"/"efg"...
> The issue got resolved when I changed this to ("abc"/"cde"/"efg"...). Now I am able to use UnaryOp.to_array. Not sure how this matters, since we are defining the method inside {..}

rule
  A / B / C { def foo; …; end }
end

defines foo only for the C path. You can even do this:

rule
  (A / B / C { def foo; …; end }) { def bar; …; end}
end

which defines foo for C, but bar for all paths. Note that
the two modules will be mixed in to the same SyntaxNode
in this case.

> Another issue I had was in accessing methods for optional non-terminals.

This is a known trap. The accessor method for C is defined
only if the rule was matched. I think this is a bug; the method
should be defined regardless, but return nil if C was not
matched. You can work around it using labels and .empty?,
because the label is always defined.

A fix for this would be welcome, if anyone has time.

Clifford Heath.


 
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