in reply to Re^8: Can I access and use UV types from perl?
in thread Can I access and use UV types from perl?

You seem to be over-complicating things. In a computer, registers and memory words hold a collection of bits (e.g. 64 bits). How we interpret those bits is up to the programmer and/or the CPU's ALU. One common way is to treat the bit pattern as as an unsigned binary number. Another common way is to treat them as a two's complement signed value - where values with the high bit set are treated as negative numbers from the point of view of comparisons etc. Other possibilities in the past have included just using one bit as a sign bit, and using one's complement.

The big advantage of two's complement as a way of representing negative numbers is that they can be added and subtracted exactly the same way as unsigned numbers, the only differences being when the overflow flag on the ALU should be set.

But we now seem to be a long way off from anything that has to do with perl.


  • Comment on Re^9: Can I access and use UV types from perl?

Replies are listed 'Best First'.
Re^10: Can I access and use UV types from perl?
by Don Coyote (Hermit) on Nov 18, 2019 at 20:55 UTC

    I have just read up on two's complement and one's complement through the link to wikipedia provided by haukex. I had not realised there was a two's complement representation as well as operation, and when I suggested the masking ideas, that the numbers being masked to produce the decimal representation were in two's complement representation. It just seemed to work.

    I may have been a little off the mark, when suggesting these were some kind of unused integers, yet I feel it is too early to dismiss the idea as just an outdated one's complement runoff.

    I really got a lot out of this thread and the responses from everybody have been very helpful and informative. It is exciting to find out new stuff and expand my knowledge. I try to keep it Perl, but the nature of computers is that it is all related in some manner.

    Perl may be DWIM, but WDIM? :)