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From: niklasb@my-deja.com
Subject: Suggestion: "typeof" keyword
Date: 1999/08/04
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Approved: Valentin Bonnard <bonnard@clipper.ens.fr>
X-Original-Date: Fri, 30 Jul 1999 21:03:55 GMT
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Suppose I'm writing a template function and II is an unknown
iterator type. How can I refer to the type one gets by
dereferencing an II object?

In many cases I could say II::value_type, but only if II is
a class that contains a typedef for value_type. What if II is
a simple pointer type? The use of the "typedef ... value_type"
convention in the standard library only highlights the need
for a more universal mechanism.

I have in mind a keyword, typeof, which would yield the type
of an expression. Like its cousin "sizeof," typeof would not
actually evaluate anything at run-time.

Does anyone else think such a keyword would be valuable? Or
is this a solution in search of a problem? Following is a
(somewhat contrived) example of how typeof might be used.


template<class II>
II FindEndQuote(II isz)
{
    typedef typeof(*isz) Ch;
    Ch quote = *isz;
    do {
        ++isz;
    } while (*isz != quote && *isz != Ch(0));
    return isz;
}

char* Foo(char* psz)
{
    return FindEndQuote(psz);
}


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