I don't think that it is that important to have unsigned_integer, but this argument against it doesn't stand up: 1) Unsigned integer is not just an arbitrary restriction on range but an important concept in its own right. Its use clarifies intent. In my opinion, for example, it is a common, though minor, programming error to use "int" rather than "unsigned int" when you intend to express cardinality of something (e.g., the size of an array). The only real justification otherwise is to allow such practical "tricks" as testing if a decreasing index is less than 0. 2) The extra data type, assuming that the design error of deriving unsigned_integer from integer is avoided, would add complexity for boost maintainers but virtually none for users. It is, after all a logical extension of the built in types -- it takes the user all of 5 seconds to understand it, if that. Good library design is user-centric. Developer-centric design is the root of a great deal of evil. Lack of development/maintenance resources is, of course, a valid argument, but this is a completely different issue than that of the evils of unnecessary complexity. 3) Normal use of an unsigned integer type will never "try" to produce a negative result -- its not a meaningful concept, so if you play by the rules it doesn't happen. You certainly would never try to negate a cardinality (how often do you write code that says "If this string contains 27 characters then I want another one containing -27 characters?). Subtraction does have to be done with care, but in most cases the issue of subtracting a larger from a smaller doesn't come up. Subtraction generally appears, sometimes subtly so, as a computation of the size of the complement of a subset within a larger set. If you are dealing with where you would want to use unsigned integers and you unwittingly do subtract a larger from a smaller value -- if your program logic does not protect you from it -- than you better have an exception. 4) If the exceptions are exceptional than in most systems it is very much more expensive to do an explicit test than to set up to handle an exception. Topher Cooper At 04:09 PM 6/2/2006, you wrote:
Unsigned integers shouldn't exist. If the programmer wants to check whether the number is greater than 0, or greater than 42, he can do it himself a lot faster than a try{} catch{} block in terms of both programming and runtime. Creating the extra datatype would add completely unnecessary complexity to the situation. Unnecessary complexity is the root of all evil. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost