Marc Santhoff wrote:
For the last 30 years or so I've been using a compiler compiler
originally written in 1964, the implementation has matured as different
pascal compilers have become available. I'm not suggesting that this is
usable in the general case, but looked at objectively it does allow me
to make gross behavioural changes fairly easily, e.g. to define novel
string properties and to embed pragmata in comments.
Beautiful. Would you mind disclosing the name of that fine tool? ;)
Meta-II, by Val Schorre. Wikipedia has an adequate description, I first
implemented it in the days of Pascal MT+ and since then have ported it
to Turbo, Topspeed, Delphi and FPC. I'm not saying I've done a
particularly good job, and will probably redo it for UTF16 (whatever the
correct FPC type is for that) at some point- possibly adding support for
Smalltalk-style keywords.
Obvious changes included saving more state to allow backtracking. Less
obvious was parsing comments as part of the syntax (which allows things
like XML and SNMP descriptions to be parsed), allowing string delimiters
to be specified and keeping the string delimiter as a string property.
Those last allow runtime behaviour of strings to vary depending on
delimiter, so for example a string expression using / as delimiter can
be used as a regex while a string lvalue using / as delimiter can be a
backref into a pattern.
Schorre or his coworkers later defined something called Tree Meta which
accumulates parsed source into a tree, and also has rules for how the
tree can be manipulated and "unparsed". I don't believe that anybody's
reimplemented it, but I'm occasionally tempted...
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
_______________________________________________
fpc-pascal maillist - fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
