[antlr-interest] Translating PASCAL (or C) into JAVA

Terence Parr parrt at jguru.com
Thu Feb 14 10:27:41 PST 2002

Hi Piet,

7 years ago, Gary Funck built a translator from an ancient language from 
the 60's similar to pascal to C if I remember.  As the others have 
stated, there are issues with equivalency of languages, but you're real 
question is "can it be done."  Emphatically yes.  The ANTLR system was 
specifically designed to aid language translators (I built the tree 
translator component to help me build 10 pass f-77 to parallel fortran 
translators back in the early 90s).

So, it's just a matter of learning the tricks.  In most general terms it 
can be summarized as follows:

1) Parse the old input file, constructing a tree representing the 
structure of the input and constructing a symbol table (that may have to 
be saved and used across parses/translations).

2) Manipulate the tree (intermediate form) in multiple passes using a 
tree grammar, slowing morphing it towards your target language.

3) When you think that your intermediate form is very close to the 
target language then you can do a simple walk of the tree spitting out 
text again.  Each action in the grammar does a small bit of the work and 
you pray that the emergent behavior results in valid output text. ;)

I think i'll start a simple faq entry on this :)

Chief Scientist & Co-founder, http://www.jguru.com
Creator, ANTLR Parser Generator: http://www.antlr.org


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