how to write a funtion in MAX

Yes, Max is a bit different in that the standard control and iteration functions don’t translate exactly. Here are a couple of pointers-

You can encapsulate a set of commands in an patcher or abstraction.

An ‘if then’ clause can be created using the ‘if’ object, but once you get more comfortable you might find yourself using the comparator objects (such as >, < , ==) in conjunction with the 'gate' or 'select'.

To do a operation repeatedly, use uzi. Uzi can output an index value for each bang, so this works kind of like a for loop. It even has a break command to stop iterating.

Read the tutorials and understand the order of operations! Do the max tutorials first, even if they seem boring (i want sound!) they will explain the control structures you will use with MSP.

Or [select] becomes your “switch” statement, allowing multiple if/then tests of what a given number might be, then doing something different for each. [route] goes a step further and can work with indexed lists. I also hardly ever use [if] but occasionally it works great for the task at hand. However, there are usually other ways you can do the same thing.

Sometimes the rightmost outlets of [select] and [route] are more useful than the others… they can allow filtering of a bunch of values easily, then dump out the unknown (but not matched) input value.

Remember that the humble “bang” can do absolutely anything and everything you want it to do, it all depends on what it connects to and in what order things happen. On that note, look into [trigger], one of the most useful and important objects… it not only keeps your logic flow proceeding in a certain order, it forces you to think about how the flow should go in the first place, which helps with your design. So the 2D representation in your patch is executed linearly, it just all happens so fast that it seems to be simultaneous. Keeping these two ideas in mind can help you organize your layout as well as how things interact, and in what order. Having experience in coding can be helpful as well as a hindrance when learning Max, but that’s all in how open you are to new ways of programming and how well you understand the connections/dissimilarities between the two.