[M3devel] The role INTEGER and subranges in Modula-3

[Elmar Stellnberger]

Am 30.05.15 um 17:13 schrieb Rodney M. Bates:
> There are no implicit type conversions.  Instead, this need is met by
> the concept of assignability.  If the abstract value is in a
> variable's range, it can be assigned to the variable.  Size changes,
> if needed, are the code generator's problem.
So what does the code generator do if there is an overflow not checked
by the predefined value range (i.e. BITS 8 FOR INTEGER instead of
BITS 8 for [0..255])
> All this drastically simplifies the language, while also allowing the ...
Yes, I understand your decision.
> likely to be commonly needed, LONGINT would have no place.  But native
> sized arithmetic is always the most efficient.  In today's world,
> there are two very common classes of use cases: 1) 32-bit arithmetic 
> is wide enough, 2) 32-bit is not wide enough, but 64-bit is.  In both
> cases, on machines of either native arithmetic size, we want the best
> efficiency.  LONGINT is for case 2, and when you further need to be
> able to run on either size of machine.  INTEGER is for otherwise.
  Well, that was exactly my argument for a language specified type
size of INTEGER, because things do not get faster if you use 64bit
integers instead of 32bit integers. CPU arithmetics perhaps but the
real bottleneck of today is the memory hierarchy - and using 64bit
integers doubles our memory need at least for scalars.
>
> Whether you believe in LONGINT or not, there is certainly no
> justification for more base integer types than two: one the native
> size of the machine and one bigger.
Yes, we really don`t need them as anything becomes 64bit or the native
word size respectively on the stack (that is why Ctypes.int works).
Memory latency should be a minor issue as long as our parameters and
parts of the activation records fit into the cache.