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000061_icon-group-sender _Mon Mar 3 15:49:08 1997.msg
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Received: by cheltenham.cs.arizona.edu; Mon, 3 Mar 1997 16:36:39 MST
Date: Mon, 3 Mar 1997 15:49:08 -0600
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From: gep2@computek.net
Subject: Re: "Re: Icon and two-dimensional matching
To: icon-group@cs.arizona.edu
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Interesting article, however:
>Icon and SNOBOL emphasize handling values rather than references
although there are 'name' operators, and don't handle sub-arrays,
substrings or sublists as pseudovariables.
SNOBOL4 absolutely DOES support substrings as a pseudovariable, as long as the
substring in question it the portion of the subject string that you're matching.
This, in fact, is the basis for ALL pattern matching in SNOBOL4!
>I'm interested in generalized macro processing, where the macro
processing becomes a method - a dynamic method - of program
language development, and that plays just as much a part in program
development as algorithm design, module design and data structure
design. One specifies the TRANSLATION of algorithms, data
specifications, ... into code. Previous passes over the text or previous
work in the same pass where rescanning is allowed, besides perhaps
transforming the text, may decorate it with tokens (roughtly, a structure
containing a source string and other information), or with trees or with
other structures and with other information. Then one has to recognize
patterns among the tag-along information and source text, and to
process it both by generating new information and transforming the
structures and data that exist.
One of the shortcomings of Icon (compared with S-BOL), IMO, is that Icon
supports neither EVAL() nor CODE(). Admittedly these are features that one
doesn't use often in most S-BOL programs, but when you -do- need them, they are
absolutely indispensable!
In the case in question, you could use the full features of S-BOL to modify the
program itself at source level, and to replace almost any desired part of it
with an "enhanced" version during program execution... even in the middle of a
statement!
Gordon Peterson
http://www.computek.net/public/gep2/