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Index › Programming Questions & Help › Syntax Questions › int constants with leading zero are OCTAL
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int constants with leading zero are OCTAL (Read 612 times)
mungbean
int constants with leading zero are OCTAL
Jan 24th, 2009, 10:24pm  
I can't find this documented/mentioned anywhere on the site so here we go...

I just had a bit of a run-around trying to work out why this array intialisation wouldn't compile:

Code:
int[] numbers = { 090, 150, 30 };


(The error message is Expecting DOT, found 'numbers')

It turns out that integer constants with a leading zero are assumed to be octal, and so "090" is illegal.  (I had a big pile of constants I'd pasted in from a spreadsheet that had leading zeros...)

Could this be added to the documentation for int maybe?  

This demonstrates the octal interpretation:

Quote:
int[] n1 = { 040, 245, 010 };

void setup() {
  for (int i = 0; i < n1.length; i++) {
    println("n1[" + i + "] = " + n1[i]);
  }
}



running it produces...

n1[0] = 32
n1[1] = 245
n1[2] = 8



Chris
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PhiLho 
Re: int constants with leading zero are OCTAL
Reply #1 - Jan 24th, 2009, 10:36pm  
It is something going back to the C language (at least), kept in C++ and still in Java (and even JavaFX, I think).
Octal notation isn't much used today, in favor of hexadecimal notation. That's probably why it wasn't mentioned in the Processing reference...
You were lucky you had illegal digits in the octal number, otherwise you would have had a subtle bug instead... Smiley
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