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

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

corrected:
uint16 joe;
uint32 count = 0;
...

Your suggested scenario

>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)

is quite a novel approach, indeed, but not sure if it would be easy to understand by people like me :)

Igor

______________________________________________________________
> Od: "om1zz" <om...@vo...>
> Komu: <fla...@li...>
> Datum: 26.05.2015 12:28
> Předmět: Re: [Flashforth-devel] For-next loop - full 16bit count?
>
>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).
>>>>>
>>
>>
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