Processing 1.0 - Processing Discourse - functional programming, currying

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Index › Programming Questions & Help › Syntax Questions › functional programming, currying

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functional programming, currying (Read 474 times)

field_of_thoughts

functional programming, currying
Jun 14^th, 2008, 6:19pm

Hello,

I wonder if there is a way to write in a bit more functional style using processing. Are closures available?
(I've been searching the site for currying, but didn't find any results).

For example, how would I write these javascript-lines in processing (assuming functional programming is possible):

function mf(b){
var fn = function(a){
alert(b+" would say "+a);
};
return fn;
};

var ae=mf('Albert');
ae('e=mc**2');

Thanks in advance!

PhiLho

Re: functional programming, currying
Reply #1 - Jun 14^th, 2008, 6:25pm

Java is an OO language, not a functional one. Functions are not first-class object, you can't even pass a reference to them as we do in C...
A common, heavy workaround is to wrap functions in anonymous (or not) classes, which is common for event callback functions, for example.
That's a point of Java I dislike, but hey, that's the way it works.

field_of_thoughts YaBB Newbies Offline Posts: 6	Re: functional programming, currying Reply #2 - Jun 14^th, 2008, 6:29pm Ah, I see .. thank you!

field_of_thoughts

Re: functional programming, currying
Reply #3 - Jun 14^th, 2008, 7:09pm

How would the syntax look like, if I wanted to use this workaround (anonymous classes) in the Processsing IDE. Is it possible at all or do I have to fall back to Java?

I've been trying some examples found in the web (http://www.unix.com.ua/orelly/java-ent/jnut/ch03_12.htm), but they didn't really work out in the Processing IDE, using something like

return new class-name ( [ argument-list ] ) { class-body }

If I used something like this within a Function inside the Processing IDE - what would I specify as the return-type of the function. This attempt didn't work:

Class make_a_class(){
return new Anonymous () {};
}

Thanks in advance!

field_of_thoughts

Re: functional programming, currying
Reply #4 - Jun 14^th, 2008, 7:30pm

Okay, I am as far as this:

void setup(){
Anonymous a = make_a_class();
a.test();
}

interface Anonymous{void test();};

Anonymous make_a_class() {
return new Anonymous(){
void test(){
print("test");
}
};
}

Unfortunately I can't get rid of the interface without processing throwing errors at me. This still doesn't feel very anonymous ;-)
Is there something like a Standard-Anonymous-Class?

Thanks in advance!

JohnG

Re: functional programming, currying
Reply #5 - Jun 14^th, 2008, 7:57pm

I think you'd have to do something like:

Code:

public interface Anonymous
{
  public void test();
} 

void setup()
{
  doAnonymous(new Anonymous() 
  {
    public void test()
    {
	println("Anonymous a");
    }
  }
  );
  doAnonymous(new Anonymous(){void test(){background(20);}});
}

void doAnonymous(Anonymous a)
{
  a.test();
}

field_of_thoughts YaBB Newbies Offline Posts: 6	Re: functional programming, currying Reply #6 - Jun 14^th, 2008, 8:44pm Okay, it works (as far as I need it), thanks!

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