Forums > MaxMSP

rollover when incrementing and decrementing a value

Jan 05 2011 | 9:26 pm

I need to variably increment and decrement a value, and have it return to the minimum value when a threshold is exceeded, and similarly, have it return to the MAXIMUM value when the mininum is exceeded.

So say my range is 1 to 16, and the current value is 16, if I increment then it should become 1. Conversely, if the value is 1 and I DECREMENT, then the value should go to 16.

The modulo operator (% ) seems to work for the incrementing case, but not for the decrementing case. Is there a good way to do this?

Jan 05 2011 | 9:52 pm

-- Pasted Max Patch, click to expand. --

Jan 05 2011 | 10:05 pm

That works well. I came up with this:

-- Pasted Max Patch, click to expand. --

Jan 05 2011 | 11:41 pm

the modulo would work for decrementing too – but it does not work for negative numbers.

try this for endless dials:

expr ((($i1%$i2)+($i2)*(($i1%$i2)==0))*($i1>=0))+(((($i1%$i2)+$i2)+(-$i2)*((($i1%$i2)+$i2)==0))*($i1<0))

where $i2 is the range of the dial.

and likewise for float.

if it is sure that you are using numbers only within a smaller/limited range then

[+ 10000]
[% 16]
[- 10000]

should also work.


Jan 18 2012 | 9:00 pm

(Necroing thread as I found a good solution)

— Pasted Max Patch, click to expand. —
Jan 18 2012 | 10:59 pm

I love these zombie threads! I see your maths+mod and raise you an [expr] to get it in one go!

[expr (($f1<0)*$f2)+$f1-($f2*int($f1/$f2))]

Jan 18 2012 | 11:11 pm

That definitely is more elegant than that monster expr above. I do a ton of research on the forum so might as well leave ‘breadcrumbs’ for the next guy!

Jan 19 2012 | 1:12 am

i can make it longer if required. :D

Jan 19 2012 | 1:18 am

*cough* That’s not something I thought I’d ever see written on the Max forum!

Jan 19 2012 | 3:08 pm

Luke’s formula can be made a bit more compact for ints:

[expr ($i1 % $i2) + ($i1<0) * $i2]

A similar technique would work for floats if the expr object supported fmod(). On Max5 fmod isn't supported, but perhaps in Max6 (not installed on this machine, so I can't check).

The C-programmer in me is delighted by abusing the Boolean comparison as an implicit typecast to int (either 0 or 1). The nicely brought up, well-behaved PASCAL programmer in me is appalled by it. If you find multiplication with a comparison expression a little weird, it's easy enough to whip up a little abstraction that does the same thing. Something like the following:

Jan 19 2012 | 8:11 pm

to my excuse, mine allows offsets, i.e. a center another than 0

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Forums > MaxMSP