Hi Jason,
Many thanks for your response and I will articulate my problem again.
My problem is that I don't understand how to apply the sequence(symbol)
in a transformation rule. Althought, I saw it in the Parslet examples
it is still a fuzzy item for me.
Therefore, I created a problem and in the solution I want to use the
sequence(symbol), if possible.
Let the expression be: { :result => [{ :w => "a" }, { :x => "b" } , { :y
=> "c", :z => "d"} ] } . So :result => [ ... ] is a hash with :result
as a key and the array [ ... ] as a value.
I want this expression be transformed into: { :result => [ "imf",
"strauss", "kahn" ] } :-)
In the Parslet Transformation documentation it is said: "....., but you
cannot replace the array as a whole. This is the purpose of
sequence(symbol): sequence(:x) which will match all of these [ 'a',
'b', 'c' ] [ 'a', 'a', 'a' ] [ Foo.new, Bar.new ] ... "
Besides, sequence is very picky about what it consumes and what not. But
that's not defined in CLEAR way in this documentation and not
ILLUSTRATED with examples. This part of the documentation is not very
didactic.
When I consider this problem as plain Ruby code it is easy to transform
the code, but that's not the solution I want. My goal to understand the
use of sequence in a transformation rule.
Cheers,
Thiel
Op 18-5-2011 21:01, Jason Garber schreef:
Thiel,
:elements gets captured and becomes available in the block's context.
If you want the output to be a hash, you have to have {:result =>
element } in the block. But then your transformation rule does
nothing, so I don't see why you'd want to.
I couldn't follow your example very well. Perhaps that's why no one
has responded yet. Try articulating your problem again if you're still
having trouble.
Jason
On Wed, May 18, 2011 at 5:55 AM, Thiel Chang <[email protected]
<mailto:[email protected]>> wrote:
Hi guys,
I am still struggling with the transformation rules.:-(
My aim is to understand the application of sequence(symbol) in
transformation rules.
So, I made a simple test to replace an array of objects in a
transformation rule.
The input tree for Transform is:
{ :result => [{ :w => "a" }, { :x => "b" } , { :y => "c", :z =>
"d"} ] }
and the transformation rule is:
rule( :result => sequence(:elements) ) { puts elements.inspect }
The new array is: [ "imf", strauss", "kahn"]
The required result should be: { :result => [ "imf", "strauss",
"kahn" ] }
I would be very glad if anyone can provide the solution(s).
Many thanks in advance,
Thiel
