Re: Compiler tool question

Eric O'Dell <eric@gadgetguru.com> wrote:
>For new operators, the user will be able to choose characters from a
>special operator character set (the usual C operator characters, plus
>some extras) or alternatively give them names that follow the same
>rules as any other variable or function identifier.


I suggest you follow the Standard ML trick of letting the user declare
any binary function to be infix with specified precedence and
associativity. Your parser should just suck in a list of tokens and
then you run a little operator-precedecnce parser in the semantic
analysis phase. For an example of such a parser that also support
prefix and postfix operators, see the appendix to
http://www.cs.virginia.edu/~nr/pubs/unparse.ps (which will appear in
SP&E). For a complete translator using this approach, see
http://www.cs.virginia.edu/~nr/toolkit/working/sml/rtl/WWW/grammar.html.


>I'd also like to
>be able to define operators that consist of more than one token, like
>the trinary "? :" operator in C, so that ... would be legal


You'd be amazed at how much haacking you can do with just binary infix
operators. For an example of defining


    mumble <== foo <quux> bar


see http://www.cs.virginia.edu/zephyr/csdl/intel.html.
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