Question

How would the following pseudocode translate into Python?

function IntNoise(32-bit integer: x)             

    x = (x<<13) ^ x;
    return ( 1.0 - ( (x * (x * x * 15731 + 789221) + 1376312589) & 7fffffff) / 1073741824.0);    

end IntNoise function  

I’m not sure about the following items: the 32-bit integer: x argument in the IntNoise call ; the <<, and the &7fffffff.

The function is a random number generator from this webpage: Perlin Noise.

Answer 1

Line by line, here are the changes:

1. function IntNoise(32-bit integer: x)

   We don’t need to declare the argument type, and prefer not to use CamelCase, so line one is:

   def intnoise(x):
   

2. The only thing wrong with the next line is the semicolon. Removing it, we get:

   x = (x << 13) ^ x
   

   x will be shifted to the left by 13 bits and then the result will be bitwise exclusive-OR-ed with the starting value of x.

3. On the next line, once again no semicolon, and the 7ffffff needs to be prefixed with 0x, thus:

   return ( 1.0 - ( (x * (x * x * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0)
   

---

Altogether, this makes:

def intnoise(x):
    x = (x << 13) ^ x
    return (1.0 - ((x * (x * x * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0)