AQL ANTLR4-grammar

Bert Verhees bert.verhees at rosa.nl
Tue Aug 25 04:34:35 EDT 2015


On 25-08-15 09:39, Bert Verhees wrote:
> I would like to know an example or description of an issue in which 
> Antlr4.5 does not work good enough in the OpenEHR context.
> I think that information can help me and other developers really a lot. 
I did some shallow research, maybe it can help answering this question

The specs say, antlr4.5 support standard regular expressions

http://meri-stuff.blogspot.nl/2011/09/antlr-tutorial-expression-language.html#LexerBasics
I guess this is not the same as full regular expressions, but what is 
missing?

Here are the language features from the various regex engines:
https://en.wikipedia.org/wiki/Comparison_of_regular_expression_engines#Language_features

It seems very natural that Antlr4.5 supports the standard 
Java-regex-engine, because that is supporting code one get for free when 
programming in Java.

Added by Antlr to the Java regex is recursion. It is described as one of 
the key grammar-features.
I am not sure, maybe, recursion in regex context is not the same as 
recursion in grammar-context.

I think, these are important issues, because, if Antlr4.5 is used, there 
is another code-base then when one of the traditional grammar tools is used.
So, if there is knowledge of shortcomings of Antlr4.5 in the OpenEHR 
context, or expected future OpenEHR context, then it is very important 
that all developers know about it, so they can avoid running into very 
expensive problems.

Bert




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