Re: Streams in Ada

[Ted Dennison<dennison@telepath.com>]

In article <tgofufwd4x.fsf@mercury.rus.uni-stuttgart.de>, Florian Weimer says...
>
>"Marin David Condic" <marin.condic.auntie.spam@pacemicro.com> writes:
>
>> But wouldn't that posit that there *was* an Ada95 implementation on a PDP-10
>> and that a Stream_Element was 36 bits?
>
>Well, the poster specifically mentioned portability, and his code does
>not work on such an architecture.  IMHO, portable code hasn't just to
>run on all platforms which exist (this could be called 'practically
>portable code'), but on all Ada implementations.

I think you meant, "all possible Ada implementations", which I would disagree
with. On the other hand, if we were to interpret this to say "on all likely
implementations", I could agree with you. I'll leave it up to others how likely
a conforming Ada95 PDP-10 implementation is.

However, this wouldn't actually have been a problem anyway, because the code I
wrote assumes that the user also has something close to the following
declarations:

type User_Element is mod 256;  -- Could be any multiple of this
for User_Element'size use 8;   -- Could be any matching multiple of this
type Byte_Array is array (<> Natural) of Byte;

And then the hard-coded 8's and 7's in the code I posted before would *really*
be "User_Element'size" and "(User_Element'size - 1)". I just used the hard-coded
8 as a short-cut for implying the above. On platforms with different byte sizes,
it is the user's "mod" and "'size" declarations that would be changed. (Are they
buying it? :-)  )

Out of curiosity, what exactly constituted a "byte" on a PDP-10?

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