signalling errors

["Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>]

    I think that changing "is an error" to "signals an error" is premature
    until the error-handler is adopted and we can actually standardize
    *which error* is signalled.

OK, technically we should probably do this after KMP has brought forth
his revised error proposal and implementation, and after we have debated
that system and the alternatives.  Everything depends on everything else
to some extent.  But I think that this issue of whether certain errors
must be detected if the user asks for safety would look the same
regardless of the details of the error handler.  I'd like to try to
reach a conclusion on this.  We can re-open this issue if the error
system ultimately adopted has some unforseen consequences.  For now,
let's just assume that distinct errors must be signalled for "too many
arguments', "too few arguments", "array access out of bounds", and
"attempt to take CAR/CDR of a non-list".

-- Scott