[REBOL] Bitwise manipulation Re:(2)

[mdb]

What's wrong with

>> to-hex 56
== #0038
>> to-hex 2037
== #07F5
>> to-hex -56
== #FFC8
>> to-hex -2037
== #F80B

Mike.

- Original Message -
From: [EMAIL PROTECTED]
Date: Wednesday, October 11, 2000 7:50 am
Subject: [REBOL] Bitwise manipulation Re:

> Hi, Phil...
> 
> [EMAIL PROTECTED] wrote:
> > 
> > An interesting one ...
> > 
> > I have a integer value that I must convert to binary:
> > 
> > Nice and easy for values <= 127
> > 
> > int1: 56
> > 
> > b1: to-binary to-block int1
> > 
> > HOWEVER, if int1 is greater than 127, say 2037, I have to 
> perform the
> > 
> > following task:
> > 
> > 2037 which is equivalent to 11011000 must be split into 
> 2 bytes as
> > 
> > follows
> > 
> > b1: -> 1000 effectively b1: to-binary to-block 8
> > 
> > b2: -> 01011000 effectively b2: to-binary to-block 24
> > 
> > Any suggestions..
> > 
> 
> Two suggestions:
> 
> 1)  Try using
> 
>big-endian: func [n [integer!] /local r] [
>r: copy #{}
>until [
>insert r to-binary to-char (n // 256)
>0 = n: to-integer n / 256
>]
>r
>]
> 
>>> big-endian 56
>== #{38}
>>> big-endian 2037
>== #{07F5}
> 
>However, *DANGER, WILL ROBINSON!*,
> 
>1.1) This assumes byte order for values requiring more than 8 
> bits.1.2) It breaks for negative values!  (Explaining why and 
> proposing a repair are left as exercises for the reader... 
> ;-)
> 
> 2)  Check your math.  Last time I looked, 2037 was odd, which 
> means that
>its binary representation MUST end in a one!  ;-)
> 
> -jn-
> 
> -- 
> ; Joel Neely  [EMAIL PROTECTED]  901-263-4460  38017/HKA/9677
> REBOL []  print to-string debase decompress #{
>789C0BCE0BAB4A7176CA48CAB53448740FABF474F3720BCC
>B6F4F574CFC888342AC949CE74B50500E1710C0C2400}
> 
> 

[REBOL] Bitwise manipulation Re:

[joel . neely]

Hi, Phil...

[EMAIL PROTECTED] wrote:
> 
> An interesting one ...
> 
> I have a integer value that I must convert to binary:
> 
> Nice and easy for values <= 127
> 
> int1: 56
> 
> b1: to-binary to-block int1
> 
> HOWEVER, if int1 is greater than 127, say 2037, I have to perform the
> 
> following task:
> 
> 2037 which is equivalent to 11011000 must be split into 2 bytes as
> 
> follows
> 
> b1: -> 1000 effectively b1: to-binary to-block 8
> 
> b2: -> 01011000 effectively b2: to-binary to-block 24
> 
> Any suggestions..
> 

Two suggestions:

1)  Try using

big-endian: func [n [integer!] /local r] [
r: copy #{}
until [
insert r to-binary to-char (n // 256)
0 = n: to-integer n / 256
]
r
]

>> big-endian 56
== #{38}
>> big-endian 2037
== #{07F5}

However, *DANGER, WILL ROBINSON!*,

1.1) This assumes byte order for values requiring more than 8 bits.
1.2) It breaks for negative values!  (Explaining why and proposing
 a repair are left as exercises for the reader...  ;-)

2)  Check your math.  Last time I looked, 2037 was odd, which means that
its binary representation MUST end in a one!  ;-)

-jn-

-- 
; Joel Neely  [EMAIL PROTECTED]  901-263-4460  38017/HKA/9677
REBOL []  print to-string debase decompress #{
789C0BCE0BAB4A7176CA48CAB53448740FABF474F3720BCC
B6F4F574CFC888342AC949CE74B50500E1710C0C2400}