Re: BNF DEFINITION - help!

<banks@iowasp.physics.uiowa.edu> wrote:
> Using character set C={a,b} write a BNF definition for the language
>consisting of all strings with odd length whose first and middle characters are
>the same.


In a yacc-like syntax:


S : a middleA a // an "a" followed by something
| a middleA b // with an "a" in the middle.
// followed by any single char.
| b middleB a // a "b" followed by something
| b middleB b // with a "b" in the middle,
// followed by any single char.
| a // I almost forgot these last two!
| b
;


middleA : a middleA a
| a middleA b
| b middleA a
| b middleA b
| a
;


middleB : a middleB a
| a middleB b
| b middleB a
| b middleB b
| b
;


-Dan
--
Dan Ellard - ellard@bbn.com -- BBN HARK Systems Corporation
--

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