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From: gyro@kestrel.edu (Scott Layson Burson)
Newsgroups: comp.lang.c++
Subject: Re: implicit conversion from a reference
Message-ID: <1991May24.054434.13218@kestrel.edu>
Date: 24 May 91 05:44:34 GMT
References: <1991May2.142710.7034@clear.com> <1991May4.040222.12992@kestrel.edu> <1991May9.155949.25063@clear.com>
Organization: Kestrel Institute, Palo Alto, CA
Lines: 35

In article <1991May9.155949.25063@clear.com> rmartin@clear.com (Bob Martin) writes:
>In article <1991May4.040222.12992@kestrel.edu> 
>	gyro@kestrel.edu (Scott Layson Burson) writes:
>
>>In article <1991May2.142710.7034@clear.com> 
>	rmartin@clear.com (Bob Martin) writes:
>
>>>It appears that the compiler is invoking the rule as stated in 12.3.2 of
>>>the ARM: "At most one user-defined conversion (Constructor or
>>>conversion function) is implicitly applied to a single value."  Thus
>>>the compiler is willing to convert Int to int& but not willing to
>>>convert Int to int since that would take two implicit steps.
>>
>>I don't understand this.  The conversion from `int&' to `int' is not
>>a user-defined conversion.  I can find no rule in the ARM that
>>explains why `Int' cannot be converted to `int'.
>>
>>However, G++ 1.37.1 doesn't like it either, so it's hard to believe
>>it's a bug.  Then again, G++ doesn't like the line `x += 5;' either.
>>
>>Can anyone explain what's going on here?
>
>Scott:
>One way to interpret the rule quoted above is that the compiler will
>either apply some implicit conversions to an object.  Or it will
>apply at most ONE user defined conversion implicitly.

That's not what I take to be the plain meaning of the sentence quoted
above.  Seems to me that either the rule is very poorly worded, or it
has been misinterpreted.

I will see if I can get clarification from the committee.

-- Scott
Gyro@Reasoning.COM