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## Re: Axiom musings...

 From: Tim Daly Subject: Re: Axiom musings... Date: Thu, 9 Jan 2020 17:47:21 -0500

```Provisos.... that is, 'formula SUCH pre/post-conditions'

A computer algebra system ought to know and ought to provide
information about the domain and range of a resulting formula.
I've been pushing this effort since the 1980s (hence the
SuchThat domain).

It turns out that computing with, carrying, and combining this
information is difficult if not impossible in the current system.
The information isn't available and isn't computed. In that sense,
the original Axiom system is 'showing its age'.

In the Sane implementation the information is available. It is
part of the specification and part of the proof steps. With a
careful design it will be possible to provide provisos for each
given result that are carried with the result for use in further
computation.

This raises interesting questions to be explored. For example,
if the formula is defined over an interval, how is the interval
arithmetic handled?

Tim

On 1/3/20, Tim Daly <address@hidden> wrote:
> Trusted Kernel... all the way to the metal.
>
> While building a trusted computer algebra system, the
> SANE version of Axiom, I've been looking at questions of
> trust at all levels.
>
> One of the key tenets (the de Bruijn principle) calls for a
> trusted kernel through which all other computations must
> pass. Coq, Lean, and other systems do this. They base
> their kernel  on logic like the Calculus of Construction or
> something similar.
>
> Andrej Bauer has been working on a smaller kernel (a
> nucleus) that separates the trust from the logic. The rules
> for the logic can be specified as needed but checked by
> the nucleus code.
>
> I've been studying Field Programmable Gate Arrays (FPGA)
> that allow you to create your own hardware in a C-like
> language (Verilog). It allows you to check the chip you build
> all the way down to the transistor states. You can create
> things as complex as a whole CPU or as simple as a trusted
> nucleus. (youtube: Building a CPU on an FPGA). ACL2 has a
> history of verifying hardware logic.
>
> It appears that, assuming I can understand Bauers
> Andromeda system, it would be possible and not that hard
> to implement a trusted kernel on an FPGA the size and
> form factor of a USB stick.
>
> Trust "down to the metal".
>
> Tim
>
>
>
> On 12/15/19, Tim Daly <address@hidden> wrote:
>> Progress in happening on the new Sane Axiom compiler.
>>
>> Recently I've been musing about methods to insert axioms
>> into categories so they could be inherited like signatures.
>> the same way that signatures are written, adding them to
>> the appropriate categories.
>>
>> But this is an interesting design question.
>>
>> Axiom already has a mechanism for inheriting signatures
>> from categories. That is, we can bet a plus signature from,
>> say, the Integer category.
>>
>> Suppose we follow the same pattern. Currently Axiom
>> inherits certain so-called "attributes", such as ApproximateAttribute,
>> which implies that the results are only approximate.
>>
>> We could adapt the same mechnaism to inherit the Transitive
>> property by defining it in its own category. In fact, if we
>> follow Carette and Farmer's "tiny theories" architecture,
>> where each property has its own inheritable category,
>> we can "mix and match" the axioms at will.
>>
>> An "axiom" category would also export a function. This function
>> would essentially be a "tactic" used in a proof. It would modify
>> the proof step by applying the function to the step.
>>
>> Theorems would have the same structure.
>>
>> This allows theorems to be constructed at run time (since
>> Axiom supports "First Class Dynamic Types".
>>
>> In addition, this design can be "pushed down" into the Spad
>> proof-related properties. A range such as [1..10] would
>> provide explicit bounds in a proof "by language definition".
>> Defining the logical properties of language statements in
>> this way would make it easier to construct proofs since the
>> invariants would be partially constructed already.
>>
>> This design merges the computer algebra inheritance
>> structure with the proof of algorithms structure, all under
>> the same mechanism.
>>
>> Tim
>>
>> On 12/11/19, Tim Daly <address@hidden> wrote:
>>> I've been reading Stephen Kell's (Univ of Kent
>>> https://www.cs.kent.ac.uk/people/staff/srk21/) on
>>> https://www.cs.kent.ac.uk/people/staff/srk21//blog/2014/10/07/
>>>
>>> He raised an interesting idea toward the end of the essay
>>> that type-checking could be done outside the compiler.
>>>
>>> I can see a way to do this in Axiom's Sane compiler.
>>> It would be possible to run a program over the source code
>>> to collect the information and write a stand-alone type
>>> checker. This "unbundles" type checking and compiling.
>>>
>>> Taken further I can think of several other kinds of checkers
>>> (aka 'linters') that could be unbundled.
>>>
>>> It is certainly something to explore.
>>>
>>> Tim
>>>
>>>
>>> On 12/8/19, Tim Daly <address@hidden> wrote:
>>>> The Axiom Sane compiler is being "shaped by the hammer
>>>> blows of reality", to coin a phrase.
>>>>
>>>> There are many goals. One of the primary goals is creating a
>>>> compiler that can be understood, maintained, and modified.
>>>>
>>>> So the latest changes involved adding multiple index files.
>>>> These are documentation (links to where terms are mentioned
>>>> in the text), code (links to the implementation of things),
>>>> the signatures of lisp functions), figures (links to figures),
>>>> and separate category, domain, and package indexes.
>>>>
>>>> The tikz package is now used to create "railroad diagrams"
>>>> of syntax (ala, the PASCAL report). The implementation of
>>>> those diagrams follows immediately. Collectively these will
>>>> eventually define at least the syntax of the language. In the
>>>> ideal, changing the diagram would change the code but I'm
>>>> not that clever.
>>>>
>>>> Reality shows up with the curent constraint that the
>>>> compiler should accept the current Spad language as
>>>> closely as possible. Of course, plans are to include new
>>>> constructs (e.g. hypothesis, axiom, specification, etc)
>>>> but these are being postponed until "syntax complete".
>>>>
>>>> All parse information is stored in a parse object, which
>>>> is a CLOS object (and therefore a Common Lisp type)
>>>> Fields within the parse object, e.g. variables are also
>>>> CLOS objects (and therefore a Common Lisp type).
>>>> It's types all the way down.
>>>>
>>>> These types are being used as 'signatures' for the
>>>> lisp functions. The goal is to be able to type-check the
>>>> compiler implementation as well as the Sane language.
>>>>
>>>> The parser is designed to "wrap around" so that the
>>>> user-level output of a parse should be the user-level
>>>> input (albeit in a 'canonical" form). This "mirror effect"
>>>> should make it easy to see that the parser properly
>>>> parsed the user input.
>>>>
>>>> The parser is "first class" so it will be available at
>>>> runtime as a domain allowing Spad code to construct
>>>>
>>>> One plan, not near implementation, is to "unify" some
>>>> CLOS types with the Axiom types (e.g. String). How
>>>> this will happen is still in the land of design. This would
>>>> "ground" Spad in lisp, making them co-equal.
>>>>
>>>> Making lisp "co-equal" is a feature, especially as Spad is
>>>> really just a domain-specific language in lisp. Lisp
>>>> functions (with CLOS types as signatures) would be
>>>> avaiable for implementing Spad functions. This not
>>>> only improves the efficiency, it would make the
>>>> BLAS/LAPACK (see volume 10.5) code "native" to Axiom.
>>>> .
>>>> On the theory front I plan to attend the Formal Methods
>>>> in Mathematics / Lean Together conference, mostly to
>>>> know how little I know, especially that I need to know.
>>>>
>>>> Tim
>>>>
>>>>
>>>>
>>>> On 11/28/19, Jacques Carette <address@hidden> wrote:
>>>>> The underlying technology to use for building such an algebra library
>>>>> is
>>>>> documented in the paper " Building on the Diamonds between Theories:
>>>>> Theory Presentation Combinators"
>>>>> http://www.cas.mcmaster.ca/~carette/publications/tpcj.pdf [which will
>>>>> also be on the arxiv by Monday, and has been submitted to a journal].
>>>>>
>>>>> There is a rather full-fledged prototype, very well documented at
>>>>> https://alhassy.github.io/next-700-module-systems/prototype/package-former.html
>>>>>
>>>>> (source at https://github.com/alhassy/next-700-module-systems). It is
>>>>> literate source.
>>>>>
>>>>> The old prototype was hard to find - it is now at
>>>>> https://github.com/JacquesCarette/MathScheme.
>>>>>
>>>>> There is also a third prototype in the MMT system, but it does not
>>>>> quite
>>>>> function properly today, it is under repair.
>>>>>
>>>>> The paper "A Language Feature to Unbundle Data at Will"
>>>>> (https://alhassy.github.io/next-700-module-systems/papers/gpce19_a_language_feature_to_unbundle_data_at_will.pdf)
>>>>>
>>>>> is also relevant, as it solves a problem with parametrized theories
>>>>> (parametrized Categories in Axiom terminology) that all current
>>>>> systems
>>>>> suffer from.
>>>>>
>>>>> Jacques
>>>>>
>>>>> On 2019-11-27 11:47 p.m., Tim Daly wrote:
>>>>>> The new Sane compiler is also being tested with the Fricas
>>>>>> algebra code. The compiler knows about the language but
>>>>>> does not depend on the algebra library (so far). It should be
>>>>>> possible, by design, to load different algebra towers.
>>>>>>
>>>>>> In particular, one idea is to support the "tiny theories"
>>>>>> algebra from Carette and Farmer. This would allow much
>>>>>> finer grain separation of algebra and axioms.
>>>>>>
>>>>>> This "flexible algebra" design would allow things like the
>>>>>> Lean theorem prover effort in a more natural style.
>>>>>>
>>>>>> Tim
>>>>>>
>>>>>>
>>>>>> On 11/26/19, Tim Daly <address@hidden> wrote:
>>>>>>> The current design and code base (in bookvol15) supports
>>>>>>> multiple back ends. One will clearly be a common lisp.
>>>>>>>
>>>>>>> Another possible design choice is to target the GNU
>>>>>>> GCC intermediate representation, making Axiom "just
>>>>>>> another front-end language" supported by GCC.
>>>>>>>
>>>>>>> The current intermediate representation does not (yet)
>>>>>>> make any decision about the runtime implementation.
>>>>>>>
>>>>>>> Tim
>>>>>>>
>>>>>>>
>>>>>>> On 11/26/19, Tim Daly <address@hidden> wrote:
>>>>>>>> Jason Gross and Adam Chlipala ("Parsing Parses") developed
>>>>>>>> a dependently typed general parser for context free grammar
>>>>>>>> in Coq.
>>>>>>>>
>>>>>>>> They used the parser to prove its own completeness.
>>>>>>>>
>>>>>>>> Unfortunately Spad is not a context-free grammar.
>>>>>>>> But it is an intersting thought exercise to consider
>>>>>>>> an "Axiom on Coq" implementation.
>>>>>>>>
>>>>>>>> Tim
>>>>>>>>
>>>>>
>>>>
>>>
>>
>

```