6 May 2003 01:28:25 -0400

Related articles |
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Parsing expressions without outer parentheses frank@g-n-u.de (Frank Heckenbach) (2003-04-27) |

Re: Parsing expressions without outer parentheses cfc@world.std.com (Chris F Clark) (2003-05-05) |

Re: Parsing expressions without outer parentheses slk15@earthlink.net (SLK Parsers) (2003-05-06) |

Re: Parsing expressions without outer parentheses pjj@cs.man.ac.uk (Pete Jinks) (2003-05-06) |

Re: Parsing expressions without outer parentheses hannah@schlund.de (Hannah Schroeter) (2003-05-12) |

Re: Parsing expressions without outer parentheses frank@g-n-u.de (Frank Heckenbach) (2003-05-24) |

Re: Parsing expressions without outer parentheses frank@g-n-u.de (Frank Heckenbach) (2003-05-24) |

From: | "SLK Parsers" <slk15@earthlink.net> |

Newsgroups: | comp.compilers |

Date: | 6 May 2003 01:28:25 -0400 |

Organization: | Parsers Inc. |

References: | 03-04-093 |

Keywords: | parse |

Posted-Date: | 06 May 2003 01:28:25 EDT |

*> expression: simple_expression | expression '=' simple_expression;*

*> simple_expression: term | simple_expression '+' term;*

*> term: factor | term '*' factor;*

*> factor: primary | factor '^' primary;*

*> primary: constant | '(' expression ')';*

*>*

*> Now I want to accept only expressions which are not completely*

*> enclosed in a pair of parentheses, e.g. `(1) + (2)' would be*

*> accepted, but `(1 + 2)' would not.*

Seems like this could be handled semantically. If an expression begins

with an open parenthesis, and the parentheses nesting level does not

drop to zero before the end of the expression, then "error: outer

parentheses." You need another production to delimit the

expression. Something like

expression : {action} inner_expression {action} ;

And then change expression to inner_expression in the grammar fragment shown

above.

http://parsers.org

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