Re: Do I need to invent a new type of parser?

anton@mips.complang.tuwien.ac.at (Anton Martin Ertl) writes:


>Some [extensible languages] are alive and kicking:
>Prolog allows defining any token as binary infix or unary pre- or postfix
>operator. (Some version of) ML has a similar feature. And finally there's
>Forth, where you can twist the compiler (and the syntax) as you like.


Standard ML provides infix directors for 2-ary functions, with specified
left/right associativity and precedence. Lazy ML goes further, providing
"concrete data types". These are tree-structures (like Prolog terms) with
user-defined syntax; you can add your own punctuation even when this
clashes with the keywords/punctuation of LML itself. It's handled by extra
delimiters to separate the user-defined construct from the rest of the
program, which must to a large extent avoid the problem of human
readability. Can any of the LML people comment on how useful this
construct has been? Has it been used much?


It *ought* to be useful in language-processing problems where the data
structures are abstract syntax trees. Not only compilers, but theorem
provers etc.


--
Keith Clarke
QMW, University of London.
--

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