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rotate long variable

 
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chava



Joined: 07 Sep 2003
Posts: 56

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rotate long variable
PostPosted: Tue Mar 09, 2004 1:45 pm     Reply with quote

Hello
I have a char variable, let say N, which stores a number 0-16
I also have a long variable, its name is bits
I want to set bit number "N" in the variable "bits"
i.e: when N=2 the program will set bit number 2 in the variable "bits"

I did: bits!= 1 << N;
but this works only when the value of N is <8
when N>=8 the corresponding bit of "bits" does not affected.

I also tryed "rotate_left(1,N) but this function requieres N to be a numeric element, not a variable
SteveS



Joined: 27 Oct 2003
Posts: 126

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rotate long variable
PostPosted: Tue Mar 09, 2004 2:00 pm     Reply with quote

Not elegant but:

int8 i;
bits = 1;
for( i = N; i > 0; i--) rotate_left(&bits,1);

- or -

int16 BitArray[16] = { 1, 2, 4, 8, ..... };
bits = BitArray[N];

- SteveS
Neutone



Joined: 08 Sep 2003
Posts: 839
Location: Houston

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Re: rotate long variable
PostPosted: Tue Mar 09, 2004 4:18 pm     Reply with quote

chava wrote:
Hello
I have a char variable, let say N, which stores a number 0-16
I also have a long variable, its name is bits
I want to set bit number "N" in the variable "bits"
i.e: when N=2 the program will set bit number 2 in the variable "bits"

I did: bits!= 1 << N;
but this works only when the value of N is <8
when N>=8 the corresponding bit of "bits" does not affected.

I also tryed "rotate_left(1,N) but this function requieres N to be a numeric element, not a variable


From the manual
Quote:

BIT_SET( )

Syntax:
bit_set(var, bit)

Parameters:
var may be a 8,16 or 32 bit variable (any lvalue) bit is a number 0-31 representing a bit number, 0 is the least significant bit.

Returns:
undefined

Function:
Sets the specified bit (0-7, 0-15 or 0-31) in the given variable. The least significant bit is 0. This function is the same as: var |= (1<<bit);

Availability:
All devices

Requires
Nothing

Examples:
int x;

x=5;

bit_set(x,3); // x is now 13

bit_set(*6,1); // A crude way to set pin B1 high

Example Files:
ex_patg.c

Also See:
bit_clear(), bit_test()
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