New line as whitespace and terminator











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I am parsing javascript ES6, however I can't get it to work without semicolons. I used Tin's grammar from ES5 as base , ( https://github.com/usethesource/rascal/blob/master/src/org/rascalmpl/library/lang/javascript/saner/Syntax.rsc ) and already got most of the new features from ES6, but I still can't remove the need for semicolons



Take for example:



lexical Whitespace

   = [t-nr ];



lexical LAYOUT

  = Whitespace

  | Comment

  ;



layout LAYOUTLIST

  = LAYOUT*

  !>> [t n]

  !>> "/*"

  !>> "//" ;





syntax Variable

  = VariableIdentifier {VariableDeclaration ","}+ declarations ";"



syntax Statement 

  = varDecl: Variable varDecl;


I get parsing error replacing ";" to "n" on Syntax Variable , or even creating a new rule for end of statement:



syntax EOS

= ";" | "n";


The parsing error goes to the next line after the newline.



Removing from whitespaces or from the layoutlist gives me parsing error on comments at the start of the file.



And removing on the layoutlist gives me ambiguity.






javascript grammar rascal







share|improve this question






















  • This is tricky stuff! You need a number of advanced features and a lot of thinking and debugging you get this right. I'll try and list the useful features in an answer tomorrow if I feel well enough. For now it's best to go for an ambiguous grammar first, which exactly describes js syntax input but is an over-approximation (too many) for its syntax trees. Using step-by-step grammar changes, and adding disambiguation constructs you can filter the superfluous trees. Better make a regression test set using rascals test function feature as well, to help in trusting the changes.
    – jurgenv
    2 days ago















up vote
1
down vote

favorite












I am parsing javascript ES6, however I can't get it to work without semicolons. I used Tin's grammar from ES5 as base , ( https://github.com/usethesource/rascal/blob/master/src/org/rascalmpl/library/lang/javascript/saner/Syntax.rsc ) and already got most of the new features from ES6, but I still can't remove the need for semicolons



Take for example:



lexical Whitespace

   = [t-nr ];



lexical LAYOUT

  = Whitespace

  | Comment

  ;



layout LAYOUTLIST

  = LAYOUT*

  !>> [t n]

  !>> "/*"

  !>> "//" ;





syntax Variable

  = VariableIdentifier {VariableDeclaration ","}+ declarations ";"



syntax Statement 

  = varDecl: Variable varDecl;


I get parsing error replacing ";" to "n" on Syntax Variable , or even creating a new rule for end of statement:



syntax EOS

= ";" | "n";


The parsing error goes to the next line after the newline.



Removing from whitespaces or from the layoutlist gives me parsing error on comments at the start of the file.



And removing on the layoutlist gives me ambiguity.






javascript grammar rascal







share|improve this question






















  • This is tricky stuff! You need a number of advanced features and a lot of thinking and debugging you get this right. I'll try and list the useful features in an answer tomorrow if I feel well enough. For now it's best to go for an ambiguous grammar first, which exactly describes js syntax input but is an over-approximation (too many) for its syntax trees. Using step-by-step grammar changes, and adding disambiguation constructs you can filter the superfluous trees. Better make a regression test set using rascals test function feature as well, to help in trusting the changes.
    – jurgenv
    2 days ago













up vote
1
down vote

favorite









up vote
1
down vote

favorite











I am parsing javascript ES6, however I can't get it to work without semicolons. I used Tin's grammar from ES5 as base , ( https://github.com/usethesource/rascal/blob/master/src/org/rascalmpl/library/lang/javascript/saner/Syntax.rsc ) and already got most of the new features from ES6, but I still can't remove the need for semicolons



Take for example:



lexical Whitespace

   = [t-nr ];



lexical LAYOUT

  = Whitespace

  | Comment

  ;



layout LAYOUTLIST

  = LAYOUT*

  !>> [t n]

  !>> "/*"

  !>> "//" ;





syntax Variable

  = VariableIdentifier {VariableDeclaration ","}+ declarations ";"



syntax Statement 

  = varDecl: Variable varDecl;


I get parsing error replacing ";" to "n" on Syntax Variable , or even creating a new rule for end of statement:



syntax EOS

= ";" | "n";


The parsing error goes to the next line after the newline.



Removing from whitespaces or from the layoutlist gives me parsing error on comments at the start of the file.



And removing on the layoutlist gives me ambiguity.






javascript grammar rascal







share|improve this question













I am parsing javascript ES6, however I can't get it to work without semicolons. I used Tin's grammar from ES5 as base , ( https://github.com/usethesource/rascal/blob/master/src/org/rascalmpl/library/lang/javascript/saner/Syntax.rsc ) and already got most of the new features from ES6, but I still can't remove the need for semicolons



Take for example:



lexical Whitespace

   = [t-nr ];



lexical LAYOUT

  = Whitespace

  | Comment

  ;



layout LAYOUTLIST

  = LAYOUT*

  !>> [t n]

  !>> "/*"

  !>> "//" ;





syntax Variable

  = VariableIdentifier {VariableDeclaration ","}+ declarations ";"



syntax Statement 

  = varDecl: Variable varDecl;


I get parsing error replacing ";" to "n" on Syntax Variable , or even creating a new rule for end of statement:



syntax EOS

= ";" | "n";


The parsing error goes to the next line after the newline.



Removing from whitespaces or from the layoutlist gives me parsing error on comments at the start of the file.



And removing on the layoutlist gives me ambiguity.






javascript grammar rascal




javascript grammar rascal






share|improve this question













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asked 2 days ago









Adriano Torres

133




133












  • This is tricky stuff! You need a number of advanced features and a lot of thinking and debugging you get this right. I'll try and list the useful features in an answer tomorrow if I feel well enough. For now it's best to go for an ambiguous grammar first, which exactly describes js syntax input but is an over-approximation (too many) for its syntax trees. Using step-by-step grammar changes, and adding disambiguation constructs you can filter the superfluous trees. Better make a regression test set using rascals test function feature as well, to help in trusting the changes.
    – jurgenv
    2 days ago


















  • This is tricky stuff! You need a number of advanced features and a lot of thinking and debugging you get this right. I'll try and list the useful features in an answer tomorrow if I feel well enough. For now it's best to go for an ambiguous grammar first, which exactly describes js syntax input but is an over-approximation (too many) for its syntax trees. Using step-by-step grammar changes, and adding disambiguation constructs you can filter the superfluous trees. Better make a regression test set using rascals test function feature as well, to help in trusting the changes.
    – jurgenv
    2 days ago
















This is tricky stuff! You need a number of advanced features and a lot of thinking and debugging you get this right. I'll try and list the useful features in an answer tomorrow if I feel well enough. For now it's best to go for an ambiguous grammar first, which exactly describes js syntax input but is an over-approximation (too many) for its syntax trees. Using step-by-step grammar changes, and adding disambiguation constructs you can filter the superfluous trees. Better make a regression test set using rascals test function feature as well, to help in trusting the changes.
– jurgenv
2 days ago




This is tricky stuff! You need a number of advanced features and a lot of thinking and debugging you get this right. I'll try and list the useful features in an answer tomorrow if I feel well enough. For now it's best to go for an ambiguous grammar first, which exactly describes js syntax input but is an over-approximation (too many) for its syntax trees. Using step-by-step grammar changes, and adding disambiguation constructs you can filter the superfluous trees. Better make a regression test set using rascals test function feature as well, to help in trusting the changes.
– jurgenv
2 days ago

















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