i plus plus

[David Lowenfels]

for( i=0; i<10; i++ ) {;}  //this is slow but very clear

for( i=0; i<=10; ++i ) {;} //this is faster

or if you don't need an index, just a repeat:

i = 10+1; //loop 10 times... sorta confusing
while( --i ) {;}	//this is fastest?

I think maybe people use i++ becuase it is semantically simple... no 
weird extra number stuff.

-DFL

>You got it backwards again...
>++i is faster than i++
>
>++i  is pre-assignment-increment, in other words increment and then 
>assign the value
>i++ is post-assignment-increment, in other words assign the value 
>then increment.
>
>so that means every time you use post-increment a temporary variable 
>holding the present state of the variable is created so that it can 
>be returned and the actual value incremented, this is the semantic 
>definition and how it must be implemented in any class.
>
>as an example:
>
>++i
>{
>i = i + 1;
>return i;
>}
>
>and ...
>
>i++
>{
>int j = i;
>i = i + 1;
>return j;
>}
>
>so....
>
>int i = 0;
>cout << i++;
>
>output = 0
>
>and...
>
>int i = 0;
>cout << ++i;
>
>output = 1;
>
>this behaviour only comes into play with assignments so since you 
>have the pick of the two in loops you should choose the faster one 
>which is always ++i. I have no idea why i++ is in every basic loops 
>example in every loop. I guess it must have been in a basic example 
>in the Kernigan-Ritchie book (the first book on C, by the authors of 
>C, also where that "Hello world!" example program now the standard 
>in ALL programming text books comes from!)
>
>jeffyb
>
>
>
>
>Hiroko Terasawa wrote:
>
>>Thanks Jeffyb,
>>
>>
>>>use ++i in loops instead of i++, it's pre-increment so it's faster
>>>   
>>>
>>I use i++ for coding, but when writing ...
>>...snip...
>>increment? Why does it make the code faster?
>>
>>ps. I found a treat for you...
>>http://mirror.wolffelaar.nl/zardalu.sytes.net/
>
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-- 
_/^\_/^\_/^\_/^\_/^\    Science is but a perversion of itself unless
   David Lowenfels       it has as its ultimate goal the betterment
  Vibrational Engineer   of humanity. -- Nikola Tesla
^\_/^\_/^\_/^\_/^\_/^            http://www-ccrma.stanford.edu/~dfl/