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From: rfg@NCD.COM (Ron Guilmette)
Newsgroups: comp.std.c++
Subject: Re: type/member tags (was Re: asking an object for its type)
Message-ID: <4328@lupine.NCD.COM>
Date: 10 Mar 91 03:01:14 GMT
References: <27C95D3A.1715@tct.uucp> <4201@lupine.NCD.COM> <27D270A7.2E3B@tct.uucp>
Organization: Network Computing Devices, Inc., Mt. View, CA
Lines: 26

Regarding using numeric codes for run-time type identifiers:

In article <27D270A7.2E3B@tct.uucp> chip@tct.uucp (Chip Salzenberg) writes:
>
>Why not use the class name itself?

One reason is that `class C' or `struct S' can have two or more meanings.
Each of several compilations units may define its own `class C'.

>>A much cleaner solution would have been to enlist the compiler & linker
>>to assign the globally unique "type codes" up front, prior to run-time.
>>This would have allowed us to avoid the (very expensive) table lookups
>>which we did within the kernel for each transmitted message.
>
>A string lookup though a set of strings fixed at compile time needs to
>be rewritten if it is "very expensive."

You don't understand.  If somebody charges you only $2.50 per ton of
air, it is still "too expensive".  Anything is "expensive" if you don't
really need it.

-- 

// Ron Guilmette  -  C++ Entomologist
// Internet: rfg@ncd.com      uucp: ...uunet!lupine!rfg
// New motto:  If it ain't broke, try using a bigger hammer.