🚀 go-pugleaf

jguthrie@brokersys.com wrote:
: Michel De Rosa (aliath@nyongwa.montreal.qc.ca) wrote:
: 
: : [...]
: : and/or/xor etc.. it's always been possible to do these, using the set
: : operators.. first coerce to a BITSET...
: 
: Please don't talk down to me.

Sorry it wasn't my intention to do so..

: I know how to manipulate bitsets, but do WHAT to a BITSET?

Well other posts have, i hope, already cleared that up..

: As far as I know, NONE of the M2 compilers I have ever used allow me
: to convert between any kind of number and any kind of set.

Again it may be only due to the fact that you weren't aware of the
type-coercion facility..

I've used a number of different compilers, Logitech v3 (pc/dos), JPI
TopSpeed (pc/dos), gpm-pc (again pc/dos), and an old pim2-based compiler
for VAX/VMS.. they've all allowed this sort of coercion, with some caveats,
mainly some of them would have restrictions, on a size of a set (the same
with as a cardinal), and some wouldn't allow coercing from<->to a variable
of a different size (say a bitset to a char)..

: I know that that isn't mentioned anywhere in PIM3C.

I've been at m2 for a long time (i mean real long time).. i honestly can't
say how or when i first became aware of the facility.. i know it's in Pim4,
because i recently had occasion to look it up..

I do use the term coercion, rather than casting, because there's a
difference.. the way pim4 documents the facility, absolutely no
interpretation of the bits is made.. we're forcing (coercing) the compiler
to treat the expression, as if it was of a different type.

My understanding of type-casting, suggests that there's a minimum of
interpretation being done, an attempt is made to preserve the value being
cast to another type. That is assuming we have a short-integer type,
than:

 si : SHORTINT;
 i  : INTEGER;
 ...
   si := -1;              (* On intel this maps to  FFh *)
   (* cast si to i *)
   ... at this point i should be -1 , or FFFFh...

With type-coercion, we'd likely get a positive value (always assuming
the compiler let's us cast/coerce between different bit-sizes).

   si := -1;
   i := INTEGER(si);      (* we now have  00FFh *)


Michel De Rosa
Aliath@Nyongwa.montreal.qc.ca