/prog/ - Programming in C

Name: Anonymous 2012-01-15 23:50

sup /prog/,

I'm coding in C. I have an char array that looks like this: [0,1,1,0,0,0,1,1].

How can I write this into a binary or single char so that it'll be a single variable, i.e. b = 01100011?

And then convert that back into decimal?

Name: Anonymous 2012-01-15 23:51

go eat a dick, fagstorm

Name: Anonymous 2012-01-15 23:54

How C is better than Haskell?



Lisp                        | Haskell

----------------------------|---------------------------------------------------

reduce                      | fold, foldl, foldr, foldl',

                            | foldr1, foldl1, foldl1...

----------------------------|---------------------------------------------------

map                         | map, mapM, mapM_, mapAccumL, mapAccumR, mapAccum,

                            | mapAndUnzipM, mempty, mappend, mapAccumRWithKey,

                            | mapAccumWithKey, mapMaybe, mapMaybeT mapEither,

                            | mapEitherWithKey, mapMaybeWithKey, mapFst, mapSnd,

                            | mapIndices, mapArray, mapListT, mapMonotonic,

                            | concatMap, amap, ixmap...

----------------------------|---------------------------------------------------

elt                         | fst snd thd fth ffth...

Name: Anonymous 2012-01-16 0:06

>>1
You should use bitwise shift operators.

Initialize an unsigned variable to 0. Then in a loop bitwise or with the array's element and then shift.

Name: Anonymous 2012-01-16 0:09

n = 0;

for (i = 0; i < 8; i++)

        n |= array[i] << i;

for (i = 0; i < 8; i++)

        array[i] = n & (1 << i) ? 1 : 0;

Name: Anonymous 2012-01-16 0:12

>>4
Thanks. Don't think I'm getting it though.. I have:

unsigned char p = 0;

for(int n = 0; n < (sizeof array); n++) {
p+=array[n];
p << 1;
}

But this didn't return what I wanted. What am I getting wrong?

Name: Anonymous 2012-01-16 0:17

>>6
You aren't using Haskell.

Name: Anonymous 2012-01-16 0:21

>>6

>>5 got the solution for you. You shouldn't add it. You should or it. Take a pencil and write them down. You will see the difference.
Btw, you should start from 7 and loop through 0. Don't forget that.

Name: Anonymous 2012-01-16 0:24



void Array2Char(char* arr, char* dst)

{

    (*dst) |= (arr[0] << 7);

    (*dst) |= (arr[1] << 6);

    (*dst) |= (arr[2] << 5);

    (*dst) |= (arr[3] << 4);

    (*dst) |= (arr[4] << 3);

    (*dst) |= (arr[5] << 2);

    (*dst) |= (arr[6] << 1);

    (*dst) |= (arr[7]);

}

Name: Anonymous 2012-01-16 0:24

>>8
Thanks. >>5 worked but produced the wrong outputs. (01101111 went to 246 for example)

Can you explain more what you mean by "You shouldn't add it. You should or it?"

Name: Anonymous 2012-01-16 0:33



void Char2Array(char* arr, char src)

{

    arr[0] = (src & (1 << 7)) ? 1 : 0;

    arr[1] = (src & (1 << 6)) ? 1 : 0;

    arr[2] = (src & (1 << 5)) ? 1 : 0;

    arr[3] = (src & (1 << 4)) ? 1 : 0;

    arr[4] = (src & (1 << 3)) ? 1 : 0;

    arr[5] = (src & (1 << 2)) ? 1 : 0;

    arr[6] = (src & (1 << 1)) ? 1 : 0;

    arr[7] = (src &  1      ) ? 1 : 0;

}

Name: Anonymous 2012-01-16 0:41

>>10

[q]"You shouldn't add it. You should or it?" [/q]

Consider the following:



char b = 0;

char arr[8] = {0,1,1,0,0,0,1,1};

[q]b += arr[1];[/code]
Adding 1 to b every time will just add 1 and 0 to the number. So at the end you'll end up with something like 6 or 8, when in fact arr represents 99 in binary.

[q]b |= (arr[1] << 6);[/q]



arr = 0 1 1 0 0 0 1 1 

        |

        V

b   = 0 1 0 0 0 0 0 0

With OR the bit is set in the location it needs to be set at.

Name: Anonymous 2012-01-16 0:46

Thanks for the help guys. >>5 's solution actually flipped the bit sequence but I figured it out.

Name: Anonymous 2012-01-16 1:02

bitfield struct

typedef struct {

        unsigned char bit8 :1;

        unsigned char bit7 :1;

        unsigned char bit6 :1;

        unsigned char bit5 :1;

        unsigned char bit4 :1;

        unsigned char bit3 :1;

        unsigned char bit2 :1;

        unsigned char bit1 :1;

} divisibleByte;

Name: Anonymous 2012-01-16 1:27

>>14

Hey, that's actually a pretty good idea!



int main()

{

    divisibleByte a;

    a.bit8 = a.bit7 = a.bit6 = a.bit5 = a.bit4 = a.bit3 = a.bit2 = a.bit1 = 1;

  

    printf("%d\n", *((unsigned char*)&a));

  

    a.bit8 = 0;

    printf("%d\n", *((unsigned char*)&a));

    

    return 0;

}

With GCC with no -OX flag a lot of ORs and lea is generated. On -O4 it's just something like mov edx,0xff.

Name: Anonymous 2012-01-16 2:30

use python

Name: Anonymous 2012-01-16 2:50

>>12
Quote by putting a greater-than symbol and a space before a line
Result looks like this
For inline quotes the custom is to use ``faggot quotes''.

Name: Anonymous 2012-01-16 11:00

use Racket

Name: Anonymous 2012-01-17 7:51

print array

problem????

Programming in C

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Name: Anonymous 2012-01-17 7:51