Re: surprise data from Ada.Sequential_IO

[Shark8 <onewingedshark@gmail.com>]

On Monday, March 22, 2021 at 1:41:59 PM UTC-6, Jeffrey R. Carter wrote:
> On 3/22/21 7:14 PM, John Perry wrote: 
> > 
> > For Direct_IO I inferred this fact from ARM A.8.3, "the file is viewed as a set of elements occupying consecutive positions in linear order", but I don't see a similar indication for Sequential_IO. Is there a warning in the ARM about this? 
> > 
> > (I do see the warning in Barnes' book, which I had consulted! and saw! and decided not to use Direct_IO as a result! but somehow read the same thing about Sequential_IO & either forgot or mis-concluded something. So I acknowledge my stupidity here.)
> The only differences between Direct_IO and Sequential_IO are that Direct_IO 
> allows random access and mixed input and output. In both cases the file contains 
> a sequence of binary representations of values of a single type. 
> 
> I don't really understand why Sequential_IO exists, since Direct_IO provides a 
> superset of Sequential_IO's functionality.
Going by some of the stuff where I work, most of which has foundational-stuff from the 80s and 90s (though not in Ada), the "Direct IO" is considered to be raw read/write concerning hardware or UDP datagram-packets or such. So, I would assume that by the nomenculture [and usage] of the day Direct_IO was meant for similar. Sequential_IO though sounds like a "and here we have a file full of entries of Type X, which we made generic to save ourselves the headache of maintaining multiple identical-except-for-type package."