Opaque

The opaque type is dangerous and rarely useful. However, there are particular times when an opaque type is the only way to solve a problem; for example, it is one of the few portable ways to implement an object with state in FORTRAN 77 (see Section [*]). When a SIDL file uses an opaque type, Babel guarantees only bits will be relayed exactly between caller and callee. If there is a need to pass more information than an opaque provides, than the developer can simply pass a pointer to that information.

Use of a opaque carries a heavy penalty. When Babel matures enough to support distributed computing, any method calls with opaque in the argument list (or return type) will be restricted to in-process calls only.
\begin{rationale}
Since {\ttfamily\slshape {opaque}\/} is typically used for a p...
...equence of bits has no meaning outside of its own
process space.
\end{rationale}





babel-1.4.0
users_guide Last Modified 2008-10-16

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