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

[Mikael N. <mik...@fl...>]

I added printing of the index to your pseudocode.

So     2 for r@ u. next
prints  2 1

And     0 for r@ u. next
prints  0 65535 .... 1

So will also your pseudocode below, but

I want  65535 for r@ u. next
prints  65535 .... 0

This is what I have implemented in the FOR2
You can pull it from git.

BR Mike


uint16 index;
uint16 count = 0;

index = 2;

for_loop:

blink_a_led;

count = count + 1;

print index;              <----------------NOTE

/ / decrement and skip if zero test
index = index  - 1;   /// decrement
if index==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;


On 26.05.2015 13:28, om1zz wrote:
> 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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>
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