Parsing issue

[zanyoats]

I am writing a parser for the smalltalk language and am having an problem with the following equivalent rules. One works (unaryExpr2) and the other (unaryExpr) parses short. Thanks!

ometa STParser { 
  tokRule = ...,
  primary = ...,
  unarySel = ...,
  ...
  // does not work
  unaryObjExpr  = unaryExpr | primary,
  unaryExpr = unaryObjExpr:mexpr tokRule('unarySel'):sel -> [`send, mexpr, sel],

  // works
  unaryExpr2 = (unaryExpr2 | primary):mexpr tokRule('unarySel'):sel -> [`send, mexpr, sel],
  ...
}

STParser.matchAll('56 double factorial', 'unaryExpr') =
[send, [number, 56], [selector, double]]

STParser.matchAll('56 double factorial', 'unaryExpr2') =
[send, [send, [number, 56], [selector, double]], [selector, factorial]]

[alexwarth]

Hi, Charlie The problem is that in the version that doesn't work, you have indirect left recursion, which is not supported in OMeta/JS.

[zanyoats]

Hi,
I wasn't aware of that. Thanks for your timely response. Best!

On Thu, Aug 13, 2015 at 3:09 PM, Alessandro Warth notifications@github.com
wrote:

Hi, Charlie The problem is that in the version that doesn't work, you have
indirect left recursion, which is not supported in OMeta/JS.

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~Charlie