Cart
[Home] [By Thread] [By Date] [Recent Entries]
That's correct for C (and many C-like languages), but the use of & is very language dependent - I was only using to avoid overloading "and" in the discussion. Not every language allows you to fiddle "bits" so & and && (and | and ||) aren't always needed. Rick Tei wrote: > On 12/15/06, Rick Marshall <rjm@z...> wrote: >> Hi Ken >> >> The point here is quite subtle and VERY important. >> >> Let's just take "a AND b" or "a & b" to reduce the overloading of the >> word and. >> >> Now if a and b are atomic and & is commutative the the order of >> evaluation is unimportant and optimisers can play around to suit >> themselves. >> >> However, if a or b are not atomic and the calculation of either has side >> effects then "a & b" is no longer commutative and optimisers cannot stop >> the calculation on detection of a or b being false. >> >> Unless of course we agree to use slightly different mathematics: "a & b" >> is not commutative; it is evaluated left to right; and evaluation stops >> if a is false. This can then be extended to "a & b & c ...". >> >> Now the "a & b" of computer languages is fundamentally different to the >> "a & b" of mathematics although they degenerate to the same thing if a >> and b are atomic. >> > > Just to be sure, & is different from && on C. > > & is the and operation betwen bits, the result is a integer > && is the and operation betwen booleans, the result is a boolean > > 0x0F & 0xF0 result to 0 > 0x0F && 0xF0 result to true > > You will not use & for shortcuts, but &&. > > _______________________________________________________________________ > > XML-DEV is a publicly archived, unmoderated list hosted by OASIS > to support XML implementation and development. To minimize > spam in the archives, you must subscribe before posting. > > [Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/ > Or unsubscribe: xml-dev-unsubscribe@l... > subscribe: xml-dev-subscribe@l... > List archive: http://lists.xml.org/archives/xml-dev/ > List Guidelines: http://www.oasis-open.org/maillists/guidelines.php >
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] |
