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Re: Error Signalling
Date: Sun, 29 Jun 86 18:18:21 PDT
>> It's *probably* not a portability problem that (safety 1) means something
>> different in different implementations. PCLS uses the speed settings to
>> switch various kinds of optimizations, but we didn't have much intuition
>> about what the difference between (speed 2) and (speed 3) should be
We also didn't know what should be done for the various settings of
speed, size and safety so we put the decision back in the users'
Our compiler can perform a number of optimizations, some of the
optimizations involve removing safety checks and for these we felt
that the user should be aware of what they are and should have control
over when they are done.
Therefore each optimization is controlled by a function of safety,
size and speed. The user is free to redefine the functions if he
doesn't like the default function. Here is an example of the function
which controls one of the optimizations discussed recently: that of
not checking the number of arguments passed to the function:
#'(lambda (safety size speed)
(declare (ignore size))
(or (< speed 3)
(> safety 0)))
"bound to a function which given safety, size and speed returns t
if the compiler should generate code to verify that the correct number
of arguments were passed to a function.
Note: an argument count check is always done if there are optional
or rest arguments.")
Nit: that isn't in the LISP: or USER: package, I hope, but SYS: or some
other private package.