[ragel-users] union operator and thread-local variables

Devin Bayer web at t-0.be
Thu Oct 29 08:36:19 UTC 2009

Hi Adrian:

After our discussion I think I can express this more clearly. 
Ragel works well to recognize my grammar but doesn't expose the 
primitive constructs required to determine context, which is 
important for extracting values from the input stream.

Workarounds are available but they require an unmaintainable 
amount of copy & pasting and are less efficient, since they use 
backtracking or duplication of all shared states. A macro 
language would improve the situation, but it would only hide the 

My proposal would make ragel easier to use. Constructs like 
matching text before ']]>', which the manual admits cannot be 
expressed using ragel's RE operators, would become simpler.

Each state is in one or more threads.  It doesn't require any 
runtime overhead to make this information available and I don't 
see any major hurdles with keeping track of the information in 
the compiler.  It doesn't require action rewriting, just building 
one more piece of data.

So my concern is not about implementation, but that you don't 
recognize the value of this feature.


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