ParserFilter suggestion

[John Cowan]

Ron Bourret scripsit:
 
> Currently, SetParser in ParserFilter accepts a single parser.  I think this
> should be a Stack of parsers.  Each ParserFilter would set its own parser to the
> top parser on the stack, pop that off, and pass the rest of the Stack to the
> next level down.  This would allow the application to build a stack of
> ParserFilters, each performing a different operation.

That was my intent in making ParserFilter a subinterface of Parser.
Here's how an application can do what you want:

	Parser p;
	ParserFilter pf;
	p = new RealParser();
	pf = new FooFilter();
	pf.setParser(p);
	p = pf;
	pf = new BarFilter();
	pf.setParser(p);
	p = pf;
	pf = new BazFilter();
	pf.setParser(p);
	p = pf;
	...

If setParser returned "this" rather than void, then you could write the
cascade in fewer lines:

	Parser p = new RealParser();
	ParserFilter pf = new FooFilter().setParser(p);
	pf = new BarFilter().setParser(pf);
	pf = new BazFilter().setParser(pf);
	...
	p = pf;

I will probably make that change to setParser.

-- 
John Cowan	http://www.ccil.org/~cowan		cowan at ccil.org
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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