Re: [Flashforth-devel] For-next loop - full 16bit count?

[om1zz <om...@vo...>]

A loop with "decrement and skip if zero" construct in asm means condition evaluation and action around "next"-  like this (an example code):

uint16 joe;
uint16 count = 0;

joe = 2;

for_loop:  

blink_a_led;

count = count + 1;

/ / decrement and skip if zero test
joe = joe  - 1;   /// decrement
if joe==0 goto out_of_loop // skip if zero
// end of decrement and skip if zero test

goto for_loop:   // this will be skipped when zero

out_of_loop:

print count;

end

With joe=2 the count will be 2, with joe=0 the count will be 65536.

Igor

______________________________________________________________
> Od: Mikael Nordman <mik...@fl...>
> Komu: <fla...@li...>
> Datum: 26.05.2015 11:51
> Předmět: Re: [Flashforth-devel] For-next loop - full 16bit count?
>
>If you do a decrement and skip if zero, it means that one index will 
>not be counted (=0).
>So you would not get the full 16-bit range.
>2 for ---> 2 1   (2 counts)
>1 for ---> 1     ( 1 counts)
>0 for ---> 65535 65534 .. 1 (65535 counts)
>
>So my NEXT uses decrement and skip if carry
>
>Therefore it has work like this
>2 for ---> 2 1 0 (3 counts)
>0 for ---> 0     ( 1 counts)
>65535 for ---> 65535 65534 .. 0 (65536 counts)
>
>BR Mike
>
>
>On 26.05.2015 11:21, om1zz wrote:
>> Some reasoning to mu suggestion below:
>> 1. we talking here forth - a better macro assembler
>> 2. with your scenario we move towards a primitive function with "more
>> intelligence" than one would expected from a better assembler..
>> 3. imho for-next in forth is an equivalent of "decrement and skip if
>> zero" construct, where (at least me since '82) observed the behaviour
>> when putting zero in it loops for a lot of times around :)
>> Igor
>>
>>>Hmm, the old FOR shall behave, I think:
>>>
>>>2 for ---> 1 0 (2 counts)
>>>0 for ----> 65535 65534 .. 0 (65536 counts)
>>>
>>>new ?FOR
>>>
>>>2 ?for ---> 1 0 (2 counts)
>>>0 ?for ---> skip (none count)
>>>
>>>So no change with 99,99999% of old code.
>>>I.
>>>
>>>______________________________________________________________
>>>> Od: Mikael Nordman <mik...@fl...>
>>>> Komu: <fla...@li...>
>>>> Datum: 26.05.2015 06:38
>>>> Předmět: Re: [Flashforth-devel] For-next loop - full 16bit count?
>>>>
>>>>I did some experiments with this and have now two for..next loops
>>>>: t for r@ u. next ;  ok<#,ram>
>>>>: tt for2 r@ u. next ;  ok<#,ram>
>>>>9 t 8 7 6 5 4 3 2 1 0  ok<#,ram>
>>>>9 tt 9 8 7 6 5 4 3 2 1 0  ok<#,ram>
>>>>
>>>>The only problem is the naming of the words.
>>>>The old FOR ideally should be called ?FOR
>>>>and the new one FOR.
>>>>But that introduces a problem with existing FF code...
>>>>
>>>>Mike
>>>>
>>>>On 24.05.2015 16:00, om1zz wrote:
>>>>> Yea, I do understand the zero loop skip intention, but I consider 
>>>>> that a bug.
>>>>> There is no way to do full 65536 loops with 16bit without doing 0 
>>>>> for..next.
>>>>>
>>>>> As the web knowledge says - there are only incompatible for-next 
>>>>> loops and inefficient and lazy do-loops :)
>>>>>
>>>>> I would recommnd to change the behavior to full 16bit, entering 0 
>>>>> should be the users responsibility (similar as divide by zero).
>>>>
>
>
>------------------------------------------------------------------------------
>One dashboard for servers and applications across Physical-Virtual-Cloud 
>Widest out-of-the-box monitoring support with 50+ applications
>Performance metrics, stats and reports that give you Actionable Insights
>Deep dive visibility with transaction tracing using APM Insight.
>http://ad.doubleclick.net/ddm/clk/290420510;117567292;y
>_______________________________________________
>Flashforth-devel mailing list
>Fla...@li...
>https://lists.sourceforge.net/lists/listinfo/flashforth-devel
>