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On Sun, 2013-07-21 at 11:40 +0200, Vincent Lefevre wrote: > On 2013-07-20 01:03:43 -0400, Michel Hack wrote: > > Regarding interval notation in right-to-left locales, > > Vincent Lefèvre replied to me: > > > > I know that numeric literals are witten in the same order as for > > > > left-to-right scripts, but what about the order of bounds in the > > > > pair that denotes an interval? Is the low bound the first or the > > > > leftmost element? > > > > > > The first, but I would say that the full interval literal would be > > > written left-to-right. > > > > Huh? I meant "first" in the direction of the script; if the whole > > interval is written left-to-right, then the upper bound would be > > first when reading right-to-left. Or did Vincent imply that the > > entire interval literal be considered a single numeric entity? > > > > > Otherwise the first character would be "]", not "[". > > > > Right -- the outermost character. That's the generic way > > of describing bracketing constructs. The "otherwise" is > > not justified as this would be the case regardless of the > > ordering of upper vs lower bound. > > I think you should ask some expert in right-to-left scripts. > Actually it seems that the mirroring of "[" and "]" would be > done automatically, but I'm not sure. On > I am a native speaker of Arabic (largest script with right to left). Intervals in Arabic mathematics books have their lower bound on the right and their upper bound on the left. This makes the "logical order" of Right To Left (RTL) scripts similar to that of Left To Right (LTR) scripts. In both cases, the reading of the interval, in the direction of the script, starts with the lower bound and ends with the upper bound. In both cases, the file or the memory stores the characters in the "logical order" not the "screen order". To give you an example using English written from left to right then from right to left see the following two lines. (Read the second line from right to left, character by character.) Left to right script [1,2] lower is 1 and upper is 2. .2 si reppu dna 1 si rewol [2,1] tpircs tfel ot thgiR ^ ^ last character first character I know that Farsi and Urdu use the same notation for intervals as Arabic since both languages use the same Arabic script (along with about ten other languages). I am not completely sure about Hebrew although I assume it will be the same as Arabic. I hope this clarifies the issue. -- Hossam A. H. Fahmy Associate Professor Electronics and Communications Engineering Cairo University Egypt
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