Re: Larger matrices

[Georg Bauhaus <rm.tsoh.plus-bug.bauhaus@maps.futureapps.de>]

Dmitry A. Kazakov wrote:

> Synchronization mechanisms of higher level than Ada? I am excited. You mean
> semaphores, I bet.

I don't mean semaphores. You bet.
And I said, have tasking offered with much higher level PLs.
That said, is there any direct reflection of the theory of channels
in Ada?
Is pragma No_Return a high level solution for "possibly dying
remote computation"?
Look at how they currently work around distributed tasking as criticized
by Liskov many years ago: It seems to have become a more pressing
issue-- or can be bought and sold, at least.



>> There is no EVAL or COMPILE in Ada.
> 
> Assembler has them.

Assembly language does not, of course, *have* EVAL or COMPILE
instructions.  Sure, you can GOTO EVAL, and have self modifying
code at random.  That's always interesting, but I'm sure it doesn't
convince people that assembly language is therefore high level.


>> There is no goal directed evaluation.
> 
> I saw this term only in the context of low-level image processing
> primitives. Sorry, it rings wrong bells.

The goal finding operators, e.g. assignment, of a language execute
until the expression delivers a value suitable in context (the goal
is met).
The expression involves the same type of operators, recursively.
You can make your own. Example language is Icon.
So it has backtracking built in at the expression level, i.e. not at the
roll your own level.


>> There is no function environment (no upward closures).
> 
> Procedural composition is itself low-level. Ada need not to worry about
> that low-level stuff.

O.k, function composition is not the same as a some kind of type
composition that includes the primitive opearations.
Sure.   That is a different tree, does only grow on Qi land
or on some recent extension of Haskell.

(I'd say that functionalists tend to fall victim to what
they call "fusion". Many also happily ignore controlling digital
computers.  But they call the laws of functional composition high
level, as everyone else does.)


>> There are no generators with suspension.
> 
> Hydropneumatic suspension? Sorry.

suspend/resume on expressions. Helps with non-deterministic or
arbitrary length data structures, execute on demand (lazy), etc.
You can program this in Ada by roll-your-own.


>> There is no symbol manipulation, no expression macros, no inference.
> 
> Symbol manipulation is text processing, no problem in Ada. Macros is
> low-level source text processing. We don't need that.

The point is, you can do things with Lisp macros the you cannot
do otherwise.  Are you saying that because you can do without the
power of a Lisp macro system in your programs, these macros must
therefore be part of low level languages for everyone else?


> Elaborated inference is inconsistent with maintainability if not low-level.
> Namely, if inferred things are understandable, they are trivial. If they
> are non-trivial (as in Prolog), then nobody can predict the program's
> behavior.

Well, you do not *want* to predict the program's behavior.
You want to see possible solutions, that's all.


>> There are no solvers.
> 
> Because Ada programs solve non-trivial problems. Anyway, declarative is not
> a synonym of higher level.

"Declarative" may be hyped, but by all definitions I know,
"declarative" certainly fits "higher level".  Anyway, you can
combine solvers to solve non-trivial problems using combination
operators, where each solver contributes to the solution.
No Ada style roll-your-own-solvers involved.

Another example: Throw a problem decomposition into the tuple space and
wait for it to solve the problem in some way.  Maybe stepwise.


>> There are no graphics primitives etc..
> 
> Turtle graphics must be of an extremely high level...

To me graphics primitives seem higher level than a load of
Bitmap_View.Set_Pixel(Our_Turtle.Next_Y,
                      Our_Turtle.Next_X, Color => Red);

I want to be able to say, "draw a bar chart using this set of data",
*without* programming.
Using R, to pick an approximation to high level graphics operators,
it is exactly what I do, *without* further graphics systems programming.
That's high level. (And, BTW, applicable in many domains.)


> You are making an error equating domain-specific to high level.

Like the rest of humanity continues to err by using more or less
established language. :-)

Almost all programming tasks *are* domain-specific.
High level operators from high level language just
ease the construction of many domain-specific programs. That is,
of almost all programs.  At the cost of lesser control of the hardware.
No systems programming style involved when computing "Vec . Vec"
in a high level language that supports arrays at a higher level
than does Ada.
Systems programmers revert to whatever level they can get, ADTs
for a start, and "patterns" for much of the remaining solutions.

I'm *not* saying that there is anything inherently superior in
using higher level operators and such!
Array operators are just operating at a higher level than single
array cell manipulation will do.  So, typically, Ada programmers
with rely on a call to some roll-your-own "*" for arrays.

If I had wanted to say, "high level type system", where high level
refers to properties such as thread of control, the order of
possible calls established by the acceptor protocol, and so on,
I had said so.


> It is
> usually reverse. Domain-specific languages are of very low level, because
> they translate straightforwardly into the engine, which plays the role of
> the hardware. This is low-level.

This is just two solution layers close to each other, and both at a high
level. By a not uncommon definition, at least.  If I say,
 Result <- M1 {times} M2
and the parallel vector APL engine translates this into a smart
distributed algorithm,  and the result arrives within time bounds,
and the operator {times} with all the magic is *builtin*, and
is portable, and adapts to the execution environment, I call that
high level.

>  Describe a set of tables sharing some property in SQL.

A high level PL expression would be

 "make X persist",

provided this expression alone achieves persistence *without*
further programming.
No database systems programming needed such as invoking SOCI,
ODBC, writing a user defined ADT for Embedded Snorkle or whatever.



> In terms of abstraction level, most of domain-specific languages stop where
> FORTRAN-IV began. That's why there is no 5GL, 6GL, 7GL... The idea was
> wrong.

So their idea was wrong (where the 5GL is usually though of as logic
and constraints), yours are right?  Might be, but could you please chose
a good set of fresh words and avoid speaking of "high level languages"
when you are referring to something else?


>> Use a language that allows you to say,
>> using *builtin* operators, things like
>>
>>    "Give me all blocks of neighbours no more than two edges apart."
>>
>> That's high level.
> 
>    procedure Give_Me_All_Blocks...;
> 
> This is not high level, and I know the price.

Exactly, the Ada example is lower level, and requires
an implementation subprogram.
Ada doesn't offer the high level given in the phrase above.


> Domain-specific languages are
> usable in domain-specific cases ... and unusable universally.

Most high-level languages are demonstrably usable universally.
They need not be restricted to specific cases in some domain.
And certainly, SQL is not representative of the higher level languages.