Coding 1k Intro

[Stonemonkey]

I'm unsure how the compiler will deal with this:

Code: [Select]

temp = (temp+1)%2048;

As I don't think there's an ASM Mod instruction, you could try &2047 instead since it's a power of 2 which will do the same thing but the compiler might already be doing that.

[va!n]

@Stonemonkey:
thanks for the great & instead using % trick... it really saved me 21 bytes in the packed version! O.O   *kewl* 


Edited:
Atm i am using

Code: [Select]

temp = (temp+=1)&2047;


[Stonemonkey]

You're welcome, good that it helped but remember it will only work when it's powers of 2.

[Stonemonkey]

I take it

Code: [Select]

temp = (temp+=1)&2047;

works out the same as

Code: [Select]

temp = (temp++)&2047;

EDIT:
why is it not

Code: [Select]

temp=(temp+1)&2047
?

[va!n]

changed it to:

Code: [Select]

temp = (temp+=1)&2047;

... but seems there is no size different between temp+1 and temp++

[Jim]

You mustn't use either of these two lines.  It's invalid C because the value of temp is modified twice in the same expression (ie, temp+=1 is an assignment, and so is temp=).  The compiler might well compile it, and it might well do what you want, but it's wrong.

Code: [Select]

temp = (temp+=1)&2047;
temp = (temp++)&2047;

You should do this:

Code: [Select]

temp++;
temp&=2047;

This expression is silly:

Code: [Select]

buffer[x+ ((y+70)*640) ]=

Because x only ever goes up by 1, you can have outside the loop.
unsigned int *buffer_ptr = buffer+70*640;
Then, inside the loop, you can just do

Code: [Select]

*buffer_ptr++ =

Jim