[boost] [optional] Doc Nit

Subject: [boost] [optional] Doc Nit
From: Dave Abrahams (dave_at_[hidden])
Date: 2012-10-26 19:00:56

> A typical approach is to consider the existence of a
> valid return value as a postcondition, so that if the
> function cannot compute the value to return, it has
> either undefined behavior (and can use assert in a
> debug build) or uses a runtime check and throws an
> exception if the postcondition is violated. This is a
> reasonable choice for example, for function (A),

This is possibly technically correct, but confusing.  Undefined behavior
results from precondition violations, not postcondition violations.

I'd suggest:

One approach is to make a non-negative argument a precondition, so when
violated the function has undefined behavior (and can use assert in a
debug build).  Alternatively, one can use a runtime check and specify
that an exception is thrown if the postcondition cannot be
satisfied. These are a reasonable choice for example, for function (A),

I'm not sure the first sentence is quite right for your needs, but I'm
out of time to improve it further.

-- 
Dave Abrahams
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