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Bernhard (4508)

https://www.xing ... hard_Schmalhofer

A freelance software engineer with experience in webapplications, databases and bioinformatics.

A contributor to Parrot and the person behind Pipp.

A physicist who worked with third sound in Helium-III and CCD X-ray detectors.

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Journal of Bernhard (4508)

Sunday January 06, 2008
01:30 PM

Parrot Abstract Syntax Tree in Scheme-XML

[ #35308 ]

As I'm hacking away at Eclectus, Scheme on Parrot in Scheme, I'm starting to pick some Scheme knowledge. So before implementing new features I employed my new wisdom and did some refactoring on my Scheme code.

The most nasty thing in compiler.scm was the generation of PIR while traversing the to-be-compiled s-expression. I decided to use XML Infoset as an intermediate representation, as I already have an XSLT sheet for generating a PIR representation of PAST from an XML representation of PAST. The nice thing is that the XML infoset can also be represented as a Scheme s-expression, that is SXML. The Scheme librarx SSAX-SXML can turn SXML into XML and perform XSLT operations.

For an example let's look at the Scheme form:

(fx+ (fx+ -10 11) (fx+ (fx+ 4 3) (fx+ 3 3)))

In Perl 5 this could be expressed:

say ( (-11 10) + ( (4 + 3) + (3 + 3)));

Represented as SXML this becomes: (|PAST::Stmts| (|PAST::Op| (|@| (pasttype "call") (name "say")) (|PAST::Op| (|@| (pirop "n_add")) (|PAST::Op| (|@| (pirop "n_add")) (|PAST::Val| (|@| (value -10) (returns "EclectusFixnum"))) (|PAST::Val| (|@| (value 11) (returns "EclectusFixnum")))) (|PAST::Op| (|@| (pirop "n_add")) (|PAST::Op| (|@| (pirop "n_add")) (|PAST::Val| (|@| (value 4) (returns "EclectusFixnum"))) (|PAST::Val| (|@| (value 3) (returns "EclectusFixnum")))) (|PAST::Op| (|@| (pirop "n_add")) (|PAST::Val| (|@| (value 3) (returns "EclectusFixnum"))) (|PAST::Val| (|@| (value 3) (returns "EclectusFixnum")))))))))

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