John Cowan <cowan_at_ccil.org> writes:
> However, what still remains anomalous is the fact that a compound
> condition can have components r, s, such that type(r) is a subtype of
> type(s). Call such components "overlapping". Overlapping components make
> it hard to reason about the model: there are first-class components that
> are visible and second-class ones that are not. Second-class components
> shouldn't exist.
Both r and s are visible through `condition->list'.
> 3) make-compound-condition intelligently merges the field lists of the
> overlapping conditions
> [...] Choice 3 is closest to The Right Thing
The `condition' form in R5.91RS did something like this, but Andre van
Tonder and practical experience have convinced me that it's not
necessary, and introduces too much complexity.
When the situation you describe happens, there's simply an
overabundance of information about the problem. `condition-ref'
applied to the compound condition only lets you look at at one of the
components of a given type, and that's (in my experience) usually
sufficient. If you really want all the gory details,
`condition->list' will extract them.
--
Cheers =8-} Mike
Friede, V?lkerverst?ndigung und ?berhaupt blabla
Received on Fri Mar 02 2007 - 11:59:47 UTC