Re: First/Follow sets in Recursive Descent Parsers

ralph@inputplus.demon.co.uk (Ralph Corderoy)
8 Aug 2001 01:07:55 -0400

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From: ralph@inputplus.demon.co.uk (Ralph Corderoy)
Newsgroups: comp.compilers
Date: 8 Aug 2001 01:07:55 -0400
Organization: InputPlus Ltd.
References: 01-08-029
Keywords: parse
Posted-Date: 08 Aug 2001 01:07:54 EDT

Hi,


> integral = '\int' [subscript superscript] '{' expression 'd' VARIABLE '}'.
>
> The problem I have is when parsing an integral: during the parse, I
> want the letter 'd' to have a new meaning, namely to designate the
> end of the expression and indicate the variable to integrate. This
> should only be the case when parsing an integral and normally it
> should be treated as a simple variable.


In your recursive descent parse set/clear a flag that indicates the {}
part of an integral is being parsed and have the flex lexer use this
when scanning a-z to determine if d is a variable or an integral
delimeter.




Ralph.


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