Salut nicolas :)
> For positive integers, we have an infinite serie of 0 bits, but we
> don't care, we just don't print them.
> The problem with two complement is that you have an infinite serie of
> leading 1 bits...
Yes :)
> Otherwise, you can access the bit at any rank with bitAt:
> For example, you could use
> bitRepresentation
> ^(self digitLength * 8 + 1 to: 1 by: -1) collect: [:i | Character
> value: $0 charCode + (self bitAt: i)] as: String
Included in my question is the fact that small integer are encoded on 31 bits
(may be I'm wrong)
so printing 32 bits represent LargeINteger and so far I want small integetr so
was my assumption correct?
and what would be a good method to return bitString of a Small Integer.s
2 raisedTo: 29
returns 536870912
536870912 class
returns SmallInteger
2 raisedTo: 30
returns 1073741824
1073741824 class
returns LargePositiveInteger
-1073741824 class
returns SmallInteger
2 class maxVal
returns 1073741823
-1 * (2 raisedTo: (31-1))
returns -1073741824
(2 raisedTo: 30) - 1
returns 1073741823
>
> The first bit will aways be the sign with the + 1 trick.
>
> Nicolas
>
> 2011/7/4 Sven Van Caekenberghe <[email protected]>:
>>
>> On 04 Jul 2011, at 20:16, Stéphane Ducasse wrote:
>>
>>> I would like to see the two complement representation of numbers.
>>
>> This is what I do, for reading/writing unsigned or two complement signed
>> integer from/to byte streams.
>>
>> Note that two complement is only defined for a specific number size, 8, 16,
>> 32 bits.
>>
>> unsignedToSigned: integer size: size
>> ^ integer < (2 raisedTo: size - 1)
>> ifTrue: [ integer ]
>> ifFalse: [ (self twoComplement: integer size: size) negated ]
>>
>> signedToUnsigned: integer size: size
>> ^ integer negative
>> ifTrue: [ self twoComplement: integer size: size ]
>> ifFalse: [ integer ]
>>
>> twoComplement: integer size: size
>> | mask |
>> mask := (2 raisedTo: size) - 1.
>> ^ mask bitAnd: ((integer abs bitXor: mask) + 1)
>>
>> These are also very handy in this context (I believe I once submitted that
>> as an issue):
>>
>> integerFromByteArray: bytes
>> | integer |
>> integer := 0.
>> bytes withIndexDo: [ :each :index |
>> integer := integer + (each bitShift: (bytes size - index) *
>> 8) ].
>> ^ integer
>>
>> and Integer>>#asByteArrayOfSize:
>>
>> Once you have a byte representation, you can render it as bits as well.
>>
>> Sven
>>
>>
>>
>>
>
