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From: "Bradd W. Szonye" <bradds@concentric.net>
Subject: Re: const int& or int const&
Date: 1998/02/06
Message-ID: <6batt7$dph@examiner.concentric.net>#1/1
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Martin Neimeier wrote in message <34D8AD3C.5C38416B@heidelbg.ibm.com>...
>What is the difference between the three method-headers ?
>
>void foo(const in& foo_var);
>void foo(int const& foo_var);

These two are the same, and mean "reference to constant integer."

>void foo(const int const& foo_var);

This is ill-formed as written; redundant cv-qualifiers are not allowed
except as the by-product of a typedef or template instantiation. (The
cv-qualifiers, in case you are unfamiliar, are "const" and "volatile."
They are redundant in this example because both consts modify "int.")

The rule of thumb is that "const" modifies the syntactic element
immediately to its left. The major exception is that "const" written
left of the declared type modifies the element to its right (the type):

    brackets indicate const grouping
    [const int] *
    [int const] *
    [int const int] * // illegal
    [int const] [* const]

By the way, I prefer the "T const &" syntax myself; it works better with
text processing tools and is easier to explain than the full rule, which
has an exception.

Is this a FAQ? It seems to be a common question recently. I know I've
seen it in exactly this form before.

Bradd W. Szonye
bradds@concentric.net
http://www.concentric.net/~Bradds
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