Array of boolean

void main()
{
boolean number[8] ;

}

is this the proper way to declare an array of boolean characters?


Thanks

Yes, except it's normally written as bool, not boolean.

Arrays of bools are horibly inefficient. Use bitpacking instead. Each bool is a byte, while a byte can be used to store 8 boolean values as bits. That's a size savings of 8:1!

hey, could you please briefly (or not) explain how to do the bitpacking thing?

unsigned char Number;

(Number & 1) Get 1:st bit out of Number
(Number & 2) Get 2:nd bit out of Number
(Number & 4) Get 3:rd bit out of Number
(Number & 8) Get 4:th bit out of Number
(Number & 16) Get 5:th bit out of Number
(Number & 32) Get 6:th bit out of Number
(Number & 64) Get 7:th bit out of Number
(Number & 128) Get 8:th bit out of Number

Ex:
if(Number & 1) cout << "First bit is true";
if(!(Number & 4)) cout << "Third bit is false";

Setting a bit:

(Number | 1) Set 1:st bit in Number
(Number | 2) Set 2:nd bit in Number
(Number | 4) Set 3:rd bit in Number
(Number | 8) Set 4:th bit in Number
(Number | 16) Set 5:th bit in Number
(Number | 32) Set 6:th bit in Number
(Number | 64) Set 7:th bit in Number
(Number | 128) Set 8:th bit in Number

Toggle a bit:

(Number ^ 1) Toggle 1:st bit in Number
(Number ^ 2) Toggle 2:nd bit in Number
(Number ^ 4) Toggle 3:rd bit in Number
(Number ^ 8) Toggle 4:th bit in Number
(Number ^ 16) Toggle 5:th bit in Number
(Number ^ 32) Toggle 6:th bit in Number
(Number ^ 64) Toggle 7:th bit in Number
(Number ^ 128) Toggle 8:th bit in Number


In assembler, you can do much more efficient bitpacking but I guess most of you don't care about assembler (C++ board).

umm.. how would you declare that and use it? I'm looking to use a similar idea for a project for school...

would it be like

Code:

---

main()
{
 int a;
 
 // sets first to true
 a ^ 1
 // all the rest are false still
 if (a | 1)
 printf("a is true");
 else
 printf("a is false");
}

---

No, the '^' is XOR. It toggles bits so you must use '|' to set it and you must write:

a ^= 1;

and not just 'a ^ 1' because that is removed by your compiler because it doesn't do anything.

The rest of the bits in 'a' can be anything. You have to initialize it to 0 to be sure it is 0.

This loop sets all the bits in a byte:

Code:

---

unsigned char a;
long b = 1; //The lowest bit is set
for(long i = 0; i < 8; i++)
{
 a |= b; //Set the bit
 b <<= 1; //Go to the next bit
}

---

Wow! I have never seen the 'b<<=1' operator before. Cool! :cool: Multiplies with 2, right?

Yes, it's the same as moving all bits to left one step.

(00001 << 1) = 00010

In that way I can set all the bits in the byte.

Well
0x00000001 XOR 0x000000001 is 0x00000000

I think it's about time
we stop using hex and start using 32 base.
With 64 bits comming up, hex is just as tedius to
write as binary was with 8 bits.

Base 32 ? You mean like splitting up the numbers into small 5-bit parts? Why 5-bit? Isn't it better to use base 256?