On Jun 5, 2014, at 2:22 PM, J. Leslie Turriff <[email protected]> wrote:
> On Thursday 05 June 2014 12:24:12 Jeff Senn wrote: >> On Jun 5, 2014, at 12:41 PM, Hans Aberg <[email protected]> wrote: >>> On 5 Jun 2014, at 17:46, Jeff Senn <[email protected]> wrote: >>>> That is: are identifiers merely sequences of characters or intended to >>>> be comparable as “Unicode strings” (under some sort of compatibility >>>> rule)? >>> >>> In computer languages, identifiers are normally compared only for >>> equality, as it reduces lookup time complexity. >> >> Well in this case we are talking about parsing a source file and generating >> internal symbols, so the complexity of the comparison operation is a red >> herring. >> >> The real question is how does the source identifier get mapped into a >> (compiled) symbol. (e.g. in C++ this is not an obvious operation) >> >> If your implication is that there should be no canonicalization (the string >> from the source is used as a sequence of characters only directly mapped to >> a symbol), then I predict sticky problems in the future. The most obvious >> of which is that in some cases I will be able to change the semantics of >> the complied program by (accidentally) canonicalizing the source text (an >> operation, I will point out, that is invisible to the user in many (most?) >> Unicode aware editors). > So if programmer A uses editor X to write code, and programmer B uses > editor > Y to modify the code, suddenly the compiler might start generating multiple > symbols for some identifiers, causing compiles to fail for no obvious reason. > It seems to me that "the complexity of the comparison operation is a > red > herring" is perhaps a naive view; this would produce a really high > astonishment factor. > > Leslie I think we are agreeing (and miscommunicating) — the comparison operator ON SYMBOLS is incredibly important. Of course symbols must be unique! Comparing sequences of characters in the SOURCE for equality is almost a non-issue. (Consider macros, case-insensitivty in some languages, context in languages such as C++, etc…) You illustrate the problem in your example. If I write (4 characters of source) code (because my editor uses decomposed characters): å=1 ’a’ '<combing dot above>' ‘=' ‘1’ And you look at it and think you are going to write code to access that value (and your editor uses composed characters - so you have 3 characters): å = 2 ‘<a-with-dot-above>' ‘=' ‘2’ Then we have astonishment. > > -- > "Disobedience is the true foundation of liberty. The obedient must be > slaves." --Henry David Thoreau > > _______________________________________________ > Unicode mailing list > [email protected] > http://unicode.org/mailman/listinfo/unicode _______________________________________________ Unicode mailing list [email protected] http://unicode.org/mailman/listinfo/unicode
