Re: Efficiency of code generated by Ada compilers

[Brian Drummond <brian_drummond@btconnect.com>]

On Sat, 14 Aug 2010 15:51:15 +0100, "(see below)" <yaldnif.w@blueyonder.co.uk>
wrote:

>On 14/08/2010 11:47, in article jvqc66t42m4ek5rkpj59ctu3r75fb4hln2@4ax.com,
>"Brian Drummond" <brian_drummond@btconnect.com> wrote:
>
>> I was involved with the Linn Rekursiv processor (which I'm sure at least two
>> other group regulars remember)
>
>Indeed. Though David Harland's ideas on programming language design were
>about as far removed from the Ada philosophy as it is possible to get.

I'm not so sure on *design* - the goals were largely to achieve expressive
power, to give the programmer the best abstractions; the best means of
expressing the task, instead of working around the limitations of the language.

I was reminded today of his insistence there should be no difference between
intrinsic and extrinsic notation today, when I made a record "private" and
replaced all its field accesses with accessor functions - and because the syntax
was the same, the client code worked unchanged. 

So I suggest there is at least some common ground.

But on *implementation*, or the route to achieving those goals; absolutely!
Everything was to be done at runtime, by the hardware, rather than at compile
time. Including strict typing, or indeed any typing at all! 

And with _some_ justification - an Ada compiler at the time was not a trivial
task, to write or even to run... while the compilers of his were simple in the
extreme, ultimately supporting a language (called Lingo, long before Macromedia
borrowed the name) with a very compact grammar. This could be compiled to an
instruction set of eleven instructions. 

I won't claim any great merit in that simplicity, but it did allow a team of six
or seven people at its largest to develop the whole lot; from compilers through
microcode to chipset to circuit board. I wonder how many people worked on Ada...

>> There was much talk then of "bridging the semantic gap" between high level
>> languages and the low level operations in hardware. It seems we have
>> subsequently bridged the semantic gap, by leaning to program in C...
(ack! should have read: learning to program in C)

>One of our subject's many self-inflicted tragedies (c.f. the apparently
>pervasive ignorance about the Burroughs architecture).

I never had the chance to work on those, though I remember lectures on them.
Perhaps we need a Burroughs B5000 emulator; it would probably fit on a
medium-sized Spartan-3 FPGA...

- Brian