🚀 go-pugleaf

In article <JAN.92Dec15131734@pallas.neuroinformatik.ruhr-uni-bochum.de>, jan@pallas.neuroinformatik.ruhr-uni-bochum.de (Jan Vorbrueggen) writes:
> In article <1992Dec14.203631.16388@CSDNewsHost.Stanford.EDU> 
> andy@SAIL.Stanford.EDU (Andy Freeman) writes:
> 
>    Does anyone know why they preferred even/odd to >=0/<0?  Sometimes one
>    has to test the sign bit, so why not use it whenever one can use any
>    bit to split things into two classes?
> 
> Part of the reason might be that this distinction (>=0/<0) is used
> in a number of places to distinguish a system address, which has the
> MSB set, from other data, eg. a PID; this is used in I/O completion:
> if <0, the PID cell is reinterpreted as a routine in system space
> to call, as this I/O has been started by some system component and 
> not a user process.)
> 

No, No, No... It was in BLISS before the vax was speced, let allone VMS written.

The pain of 0/~=0 is that you have a horror session in getting ~true to always
be false and visa versa. To parody some user code from a vax system...

TRUE  = byte 1
False = byte 0   IBMs don't have bits, and we must be 'standard'
...
foo = ~TRUE      foo now contains 376 oct, not 0
...
if FALSE(foo)    ah hum,... oh shit...
...

Add in programers who inc/dec logicals and life can soon become a nightmare

~Paul

PS The above example is lifted from a real life PL/I system that could make
news headlines if it failed...