Looking through the April '95 DWP, I've come accross an interpretation
that I'm unsure of regarding casting using the constructor syntax:

Section 5.2.3.1 [expr.type.conv]
... If the expression list specifies a single value, the expression
is equivalent ... to the corresponding cast expression (expr.cast).

Section 5.4.4 [expr.cast]
... The conversions performed by static_cast, reinterpret_cast, const_cast,
or any sequence thereof, can be performed using the cast notation of
explicit type conversion.

Does this mean that an expression type(val) can result in a
dynamic_cast<type>(val)?  I'd thought that static_cast was the only
type of cast allowed by this syntax.

--
 Marc Sherman |  "What? Rhesus Peasus? | work mailto:marcsh@corel.ca
   CorelDRAW! | Latin. Must be Latin." | personal mailto:msherman@magmacom.com
for Macintosh |  - Edward Ka-Spel, LPD | http://www2.magmacom.com/~msherman/


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In article MAA12400@mag1.magmacom.com, Marc Sherman <msherman@mag1.magmacom.com> writes:
>Looking through the April '95 DWP, I've come accross an interpretation
>that I'm unsure of regarding casting using the constructor syntax:
>
>Section 5.2.3.1 [expr.type.conv]
>.... If the expression list specifies a single value, the expression
>is equivalent ... to the corresponding cast expression (expr.cast).
>
>Section 5.4.4 [expr.cast]
>.... The conversions performed by static_cast, reinterpret_cast, const_cast,
>or any sequence thereof, can be performed using the cast notation of
>explicit type conversion.
>
>Does this mean that an expression type(val) can result in a
>dynamic_cast<type>(val)?

No. You will notice that dynamic_cast is not listed. Dynamic_cast is
a new kind of cast, not equivalent to anything that existed before.
Old cast notation cannot invoke a dynamic_cast. (Dynamic_cast and
static_cast have some overlap. The dynamic_cast operations that cannot
be done as a static_cast cannot be invoked by an old-style cast.)

> I'd thought that static_cast was the only
>type of cast allowed by this syntax.

No. The static_cast, reinterpret_cast, and const_cast are specializations
of the old-style cast, with a little bit of overlap. The draft explains
in detail what an old-style cast means in terms of the new casts. The
wording in the latest draft has been tightened up from the April 1995
wording, but is not substantially different.

---
Steve Clamage, stephen.clamage@eng.sun.com




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