CODEWITHSUNDEEP
parsingcompiler-constructionbison
tzegian
tzegian

Reputation: 589

Different methods of implementing a specific parsing rule for a compiler

Let's say we have a rule in parsing tokens that specifies:

x -> [y[,y]*]

Where the brackets '[ ]' mean that anything in them is optional in order for the rule to take place and the * means 0 or more. e.g it could be: 

x : (empty) 
  OR
x : y 
  OR
x : y,y

as well etc. (the above are examples of input that 'x' rule would be activated, not how the code should be)

I have tried the following that works already

x : y commaY
  |
  ;

commaY : COMMA y commaY
       |
       ;

I would like to know alternative options in the above that would make it work, if there are any, for educational purposes.

Thank you in advance.

Upvotes: 1

Views: 50

Answers (1)

Bart Kiers
Bart Kiers

Reputation: 170257

EDIT my earlier answer was incorrect (as pointed out in the comments), but I cannot remove an accepted answer, so I decided to edit it.

You will need (at least) 2 rules for x -> [y[,y]*]. Here is another possibility:

x
 : list
 | /* eps */
 ;

list
 : list ',' y
 | y
 ;

Upvotes: 1

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