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From: lavinus@csgrad.cs.vt.edu
Newsgroups: comp.lang.misc
Subject: Re: The search for heterogeneous lists is still on!
Message-ID: <1076@creatures.cs.vt.edu>
Date: 1 Apr 91 18:18:16 GMT
Article-I.D.: creature.1076
References: <167:Mar3121:32:0891@kramden.acf.nyu.edu>
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Reply-To: lavinus@csgrad.cs.vt.edu ()
Organization: Virginia Tech Computer Science, Blacksburg, VA
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Hi out there!
I make no claims as to how good this example is, nor whether I might have done
this in a better way using something other than heterogeneous collections, but
here is a 'real' example:
I recently wrote a shift-reduce parser in Lisp, to parse infix mathematical
expressions.  The stack for the actual parser contains both token (terminal)
descriptions, representations of nonterminals, and integers representing
the state of the underlying FSM in the parser.  Additionally, for the code
generation portion, there is a "semantic stack" which stores the types of
variables (for variables), values of various types of constants, and
mathematical operators (+, -, etc.).  The only easy way I can see to do this
complete system in C or whatever is to either break it up into about five
different stacks, or to keep a stack of pointers of type void.

Like I say, this may not be a great example, but it does exist as an example
of a heterogeneous collection in action.  Flames graciously accepted :-).

Joe


--
_________________________________ \ ___________________________________
 Joseph W. Lavinus, Virginia Tech  \   email: lavinus@csgrad.cs.vt.edu
 1204-A University Terrace         /\  phone: (703) 552-0241
 Blacksburg, VA  24060            /  \        (703) 231-5853