Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!cai!davel
From: davel@cai.uucp (David W. Lauderback)
Newsgroups: comp.lang.c++
Subject: Re: different member functions with same arg types?
Message-ID: <1991Jan24.045312.10886@cai.uucp>
Date: 24 Jan 91 04:53:12 GMT
References: <MONTNARO.91Jan18230744@spyder.crd.ge.com> <42908@ut-emx.uucp>
Reply-To: davel@cai.UUCP (David W. Lauderback)
Organization: Century Analysis Incorporated
Lines: 79

In article <42908@ut-emx.uucp> jamshid@ut-emx.uucp (Jamshid Afshar) writes:
>In article <MONTNARO.91Jan18230744@spyder.crd.ge.com> montanaro@crdgw1.ge.com (Skip Montanaro) writes:
>>
>>I am writing a parser class for a small language. I'd like it to be able to
>>parse input from strings and files. The natural class interface (for me) is
>>something like:
>>    class parser : public ...
>>    { ...
>>	public:
>>	    parse(char *string);
>>	    parse(char *filename);
>>	...
>>    }
><text about how the compiler cannot distinguish these two, and some>
><possible fixes deleted>
>>
>>I'm open to suggestions for alternate interfaces.
>>
>>Skip (montanaro@crdgw1.ge.com)
>
>This may be overkill for what you want, but why don't you make an
>abstract class, say SourceCode, that has pure virtual functions
>for everything that a parser will want to do with some source code.
>
>class SourceCode {
>public:
>   virtual void init() = 0;
>   virtual char getChar() = 0;
>   virtual void putBackChar(char) = 0;
>   virtual void skipWhiteSpace() = 0;
>   virtual bool isAtEnd() = 0;
>   virtual void close() = 0;
>   ...
>};
>
>Then derive new classes, 'SourceFromFile' and 'SourceFromString', from
>SourceCode and implement those virtual functions however they need to
>  more suff...
>
>Jamshid Afshar
>jamshid@emx.utexas.edu

I have not use C++ very much and do not have easy access to a C++
compiler to test this out but could Skip use something like the following
code to solve his problem?

typedef	char *	FileName;

class parser : public ...
{	...
    public:
	parse(FileName filename);
	parse(char *string);
	...
}

char *test_string = "Test string";
FileName  test_file = (FileName) "TestFile";

func()
{
	class	parser	x;
	...
	x.parse("Test string");
	x.parse((FileName) "TestFile");
	x.parse(test_string);
	x.parse(test_file);
}

Or would C++ not know the difference between FileName and char *, since
there both really the same thing.  In any case, FileName could be made a
class, instead of just a typedef, to resolve the function selection problem.

Am I right here or way out in left-field?
-- 
David W. Lauderback (a.k.a. uunet!cai!davel)
Century Analysis Incorporated
Disclaimer: Any relationship between my opinions and my employer's
	    opinions is purely accidental.