Self modifying code, lambda calculus - Re: ENIAC programming

[Johnny Billquist]

On 2015-09-18 01:29, Dave G4UGM wrote:
>
>
>> -----Original Message-----
>> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Johnny
>> Billquist
>> Sent: 18 September 2015 00:12
>> To: cctalk at classiccmp.org
>> Subject: Re: Self modifying code, lambda calculus - Re: ENIAC programming
>>
>> On 2015-09-17 18:30, Dave G4UGM wrote:
>>>> -----Original Message-----
>>>> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Paul
>>>> Koning
>>>> Sent: 17 September 2015 17:02
>>>> To: General Discussion: On-Topic and Off-Topic Posts
>>>> <cctalk at classiccmp.org>
>>>> Subject: Re: Self modifying code, lambda calculus - Re: ENIAC
>>>> programming
>>>>
>>>>
>>>>> On Sep 16, 2015, at 11:36 PM, ben <bfranchuk at jetnet.ab.ca> wrote:
>>>>>
>>>>> On 9/16/2015 9:25 PM, Toby Thain wrote:
>>>>>> On 2015-09-16 6:18 PM, Dave G4UGM wrote:
>>>>>>>
>>>>>>> ...
>>>>>>> It is notable that in order to solve all problems, a computer must
>>>>>>> permit self modifying code.
>>>>>>
>>>>>>
>>>>>> Is that true? AFAIK Lambda calculus can describe any computable
>>>>>> function (as can a Turing machine), and it has no concept of "self
>>>> modifying code".
>>>>>
>>>>> I never studied any of that, but you do have to LOAD and RUN the
>>>>> program ToSolveAnythingBut42 some how so I guess that would count
>> AS
>>>> Self Modifying Code.
>>>>
>>>> "load" is an operation in a RAM stored program computer, sure.  But
>>>> self- modifying code means a program that modifies its own code
>>>> during execution.  That is a scheme that has on rare occasions been
>>>> used in
>>> history.
>>>
>>> I actually think its pretty common, at least on certain machines,
>>> especially for character manipulation.
>>> There are machines, I think the Honeywell L66 is one, which make
>>> character sting moves interruptible by updating the addresses and
>>> lengths as the instruction is executed.
>>
>> Say what? So if you run through the code/function twice, it won't work?
>> That would be pretty ugly.
>>
>
> I never said self-modifying code was petty.....

True. But while I have worked a lot on machines where you did it, and I 
have written more than my fair share of self-modifying code, I have not 
before seen a machine where the code would get modified behind your back.

Oh well. I guess I should be happen I never had to deal with that 
architecture. :-)

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol