[wg-camlp4] My uses of syntax extension

[Leo White]

>3 parsers actually.
>The original parser, the parser to patt, the parser to expr.

The original parser isn't necessary for the quotation, and of course the 
other two parsers are only both needed if you want the quotation to work as 
both a pattern and an expression.

Anyway, my point is that you do not *need* to implement quotations by 
parsing to a value and then converting to an AST fragment, in fact it is 
often easier not to.

That is not to say that some people might not want to implement their 
quotations by parsing to a value and then converting to an AST fragment. In 
fact, if they want to use an external parser (over which they have little 
control) to parse their quotations then they may have to do it that way.

For these cases I think there are three options:

1. They can implement conversion functions by hand.

2. They could use some kind of type-conv style extension to automatically 
produce the conversion functions. I'm sure such an extension would be 
welcomed by other extension authors.

3. If/when some kind of run-time type representation is added to the 
language, it could be used to create a generic conversion function.