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From: Thorsten Ottosen (tottosen_at_[hidden])
Date: 2005-12-09 16:39:43

Peter Dimov wrote:

> Thorsten Ottosen wrote:
>> Anyway, my feeling is that people that uses BOOST_NO_EXCEPTION would
>> prefer
>> if( foo() )
>> BOOST_THROW_EXCEPTION( std::exception, "MSG" );
>> where this expands to BOOST_ASSERT( "MSG" ) when BOOST_NO_EXCEPTION
>> is true.
> This very much depends on foo(). In your case I suspect that foo()
validates an input argument and the outer function is something similar
to vector<>::at.
> Think about in which circumstances one would use at() - a function
that "recovers gracefully" from input arguments out of range by throwing
an exception - as opposed to operator[], a function that uses
BOOST_ASSERT to check the input.
> Presumably, the client that calls at() _expects_ an exception when an
out of range argument is passed, and this exception is handled
somewhere; this indicates that out of range arguments to at() are
expected and this code path forms an ordinary part of the program.
> If out of range input arguments were unexpected, one would use
operator[], possibly guarded by a user-level assert.

I don't think it is that simple.

I've heard people saying they would like to use numeric_cast if it did
not throw, but did an assertion.

> To get back to throw_exception, I guess my point is that nothing is
gained by turning the throw into an assert, because people that wanted
an assert would use the asserting function, not the throwing function.

if that asserting function exists. it does not exists in many cases of
the Pointer Container library.

I think there might also be people working on platforms with exceptions
who would like to get rid of the exceptions to gain a little speed.


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