Parallel Assignments and Fuze

AlienDjinn

Posting this here for other beginners in case it helps.

I was working on a crypto program and trying to port an example from Python to handle GCD (Greatest Common Divisor) when I hit snag with my coding skills. Python has a thing called 'parallel assignment' and it's magical powers look like this:

def gcd(a,b)
// return the GCD for a and b using Euclid's algorithm.  
     while a != 0:
          a, b = b % a, a
     return b

Ok, that looks easy but conceptually stumped me. I got an alternate version to work, but it used recursion and was also clear as mud (turn on debug to see that in action below).

function gcd(a, b)
      if  b == 0  then 
          //print("DEBUG: L1 :  a  =  ", a, "  b  =  ", b, "\n") 
          a = a
      else 
          //print("DEBUG: L1 :  a  =  ",  a, "  b  =  ", b, "\n") 
          a = gcd(b, a % b)
      endif
return a

I wanted to try porting the original Python version again and finally got this to work. Thanks to a little help from https://en.wikipedia.org/wiki/Assignment_(computer_science)

function gcd(a, b)
      int  t 
      while b != 0  loop
            //print("DEBUG: L1 :  a  =  ", a, "  b  =  ", b, "\n") 
            t = a
            a = b % a
            b = t
     repeat
return a

Question: is this the preferred way to approach the concept of parallel assignment in Fuze? I'm asking because I feel like others will see examples and possibly land down this rabbit hole as well.

Apologies if this is a dumb question. Thanks for the advice.

-AlienDjinn

vinicity

I’m no expert, but I think your solution looks reasonable. Just one question: in the python example you loop while a != 0, but your code loops while b != 0. Any reason for that? It seems like it could potentially affect the answer depending on a and b’s initial value.

Edit: OK, now I noticed that you return a instead of b, which confuses me further... But If the function returns the correct values, then I guess it works?

AlienDjinn

This post is deleted!

Martin

I had to just lookup what parallel assignment even was!!

So, Fuze doesn't support it directly but if I'm understanding the article correctly then wouldn't this work?

function gcd(a,b)
    // return the GCD for a and b using Euclid's algorithm.  
    while a != 0 loop
        var t = a
        a = b % a
        b = t
     repeat
return b

I haven't tested it - and, note, it's almost identical to your verstion

AlienDjinn

@Martin @vinicity thanks for catching my transposition error from the original version. I tested that version and you're correct it works as you describe.

Well, just wanted to start this thread for others that happen along that pattern as well. Thanks!