bug#24102: Use guile variable objects as SRFI-111 boxes.

[Mark H Weaver]

Mark H Weaver <address@hidden> writes:

> As a result, some important properties of SRFI-111 boxes do not hold for
> your proposed implementation.  For example, in SRFI-111, (box? x)
> implies that (box-ref x) will not raise an exception, and this fact can
> be exploited by a compiler to produce better native code for 'box-ref'
> when the type of its argument is known to be a box.  In such cases, I
> guess 'box-ref' can be implemented as a single load instruction, whereas
> 'variable-ref' will require a conditional branch.

s/box-ref/unbox/g

     Mark