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Old October 28th 10, 04:24 PM posted to uk.railway,uk.transport.london
Sam Wilson Sam Wilson is offline
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First recorded activity at LondonBanter: Aug 2003
Posts: 173
Default More Oyster Woes ...

In article 01cb7539$ac03b1a0$LocalHost@default,
"Michael R N Dolbear" wrote:

Sam Wilson wrote


... but they are distinguishable, even in languages that do not

offer
access to the bit patterns as such.


... though I don't know of any higher-level languages that let you
distinguish between +0 and -0 integers even on hardware that supports


the distinction. (And FWIW the TCP/IP suite uses ones-complement
arithmetic in its checksum calculations.)


Fortran on the Univac/Unisys 1100 series (which used one-complement
single and double integers and indeed floating point). ...


So are you saying you could write IF (I .EQ. -0) and have it behave
differently from (I .EQ. 0) or (I .EQ. +0), or just that you could do
bitwise ops?

... IIRC the CDC
6600/7600 was the same in providing functions for bit-wise AND, OR, XOR
and NOT.


Sam