Maude-help mailing list

[Steven Eker <eker AT csl.sri.com>]

Unfortunately there is no user control over lexical issues such as 
white-space. Maude has a rather complicated definition of how to break 
text in to tokens, and in particular the seven characters: ( ) [ ] { } , 
are considered tokens in their own right, unless they are back-quoted.

User definable lexical syntax is tricky to design and even harder to 
implement; very few languages offer it - ASF+SDF is the only one of 
which I am aware - and it leads to hard-to-read programs. User definable 
lexical analysis of strings is another matter; many languages have 
external tool support for this although it can get very complicated - 
Maude itself uses flex states and custom crafted C++ for its lexical 
analyzer as its determination of whether a token is a keyword or part of 
user syntax is highly context dependent.

Steven

On 4/16/13 1:33 PM, Scott Christley wrote:
> Hello,
>
> I want my Maude (v2.3) program to be able to parse and manipulate XML.  I can 
> create sorts and operators such as this:
>
>      sort xmlValue .
>      sort xmlKey .
>      op<key>  _</key>  : xmlValue ->  xmlKey .
>
> and it works fine, but the issue is that whitespace is required between the 
> tokens, so this can be parsed:
>
> <key>  name</key>
>
> but this cannot be parsed:
>
> <key>name</key>
>
> Is there a way to allow this?  For example, it seems other symbols like 
> parentheses do not require whitespace.
>
> thanks
> Scott
>
>
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