Re: Unsignedness of std::size_t

From:

Pete Becker <pete@versatilecoding.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Sun, 15 Apr 2007 09:57:51 CST

Message-ID:

<gcOdnc1uK5fYp7zbnZ2dnUVZ8qbinZ2d@giganews.com>

Kaba wrote:

But even if it wasn't, I would still find the reasons for signed
indexes uncompelling. What is the effective difference between an
index which is less than zero and an index which is greater than
(size - 1)? Both violate the preconditions; both should produce
immediate assertions or exceptions; both are obviously wrong inside a
debugger, appearing as -k and (2^n - k) respectively.

Your example works, because the valid range is finite. Consider a
situation where the logical range is half-infinite, for example
std::vector::resize(). How do you differentiate between an accidental -1
and a very big size?

If the very big size is so large that it can't be allocated, the code
throws an exception. If it's not that large it's a valid request. The
library can't distinguish between an intentional request for UINT_MAX
objects and an accidental one.

--

    -- Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com)
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (www.petebecker.com/tr1book)

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