Re: Set operations on bool-vectors

[Stefan Monnier <monnier@iro.umontreal.ca>]

> 2013-09-21  Daniel Colascione  <dancol@dancol.org>

> 	* alloc.c (bool_vector_payload_bytes): New function: computes
> 	rounded-up payload size for a bool vector.  Always allocate
> 	at least size_t bytes even for a zero-size vector.

That should just be "New function" and the rest should be moved to
a comment in the C code.

> 	(Fmake_bool_vector): Instead of calling Fmake_vector,
> 	which performs redundant initialization and argument checking,
> 	just call allocate_vector ourselves.  Make sure we clear any
> 	terminating padding to zero.

Good.  So the functional change is to set the padding to zero.

> 	(vector_nbytes,sweep_vectors): Use bool_vector_payload_bytes
> 	instead of open-coding the size calculation.

OK that makes sense, thank you.

>>> +       doc: /* Compute A = B ^ C, bitwise exclusive or.
>> Why not make it C = A ^ B and then make C optional?
>> Same for other similar functions: make the destination argument optional.
> Then we wouldn't be able to extend these functions to accept more than
> three arguments: we wouldn't know whether the argument at the end was
> another operand or a destination.

Sounds like a minor potential inconvenience in exchange for a much
cleaner interface.


        Stefan