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Non-mathematician here. There is a discussion on this forum titled "Is “applying similar operations from left to right” a convention or a rule that forces us to mark one answer wrong?" I found it trying to answer a question I have. I could not comment as I am new here (trolling protection I guess) My interest is software localisation. My question is whether mathematics is globally written Left to Right (LTR). i.e. do those substantial countries that use a RTL languages adopt an LTR standard for mathematics (in the same way they often do when using LTR words or phrases).

Note that I am not asking what is mathematically correct (i.e. use parenthesis properly) - I am asking what is commonly actually done? Thanks

user133237
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  • What do you mean you could not add to the discussion? Which discussion? – Tobias Kildetoft Mar 05 '14 at 10:16
  • You seem to have two questions here, the one in your title, and the one about countries that use a right-to-left writing system. (I hope I interpreted your second question correctly.) I suggest rewriting this post so that it focuses more on the second question. (The way you write your first question makes it seem that you are trolling, which I'm pretty sure you are not.) – JRN Mar 05 '14 at 10:17
  • Are you asking if cultures which write from right-to-left (such as, say, Arabic or Hebrew) would evaluate expressions like $3-2-1$ from left-to-right? – JRN Mar 05 '14 at 10:20
  • I wouldn't say the convention "forces us to mark one answer wrong" but that it allows us to mark only one answer as right. – JRN Mar 05 '14 at 10:25
  • @Joel -- Good guess, I think. That would be my interpretation, too. – bubba Mar 05 '14 at 10:49
  • I did Google search for "hebrew linear algebra text" and found this linear algebra text written in Hebrew linked from the web page of the author, Amnon Yekutieli, a professor of mathematics at Ben Gurion University. The mathematical notation, even when inline, is all LTR. For example, on page 12 there is a discussion of a system where $x_1=x_2=-x_3$, where the solutions have the form $(-c,-c,c)$, written in that order, with $x_1$ on the left. – MJD Mar 05 '14 at 15:05
  • Here's the link to the question the OP is referring to: http://math.stackexchange.com/q/698886/18398 – JRN Mar 06 '14 at 00:55

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Most university-level math education has conformed to a left-to-right standard, regardless of how the native language is written. However, pre-university education differs, and it depends on the region.

For instance, see here: http://en.wikipedia.org/wiki/Modern_Arabic_mathematical_notation.

One of the reasons for the predominance of left-to-right mathematical writing is that a majority of mathematical papers are written in left-to-right languages. Furthermore, it is difficult to find equivalent texts for some (advanced) topics written in a right-to-left sense. Even translation is particularly difficult. While there might be a translation for "limit" or "derivative" in some languages, there often isn't a direct translation for something like "cotangent bundle" or "Hom functor." How does one translate an advanced text when the nomenclature is so-far removed from the native language? (One may even argue that some of the nomenclature is pretty far removed from English, as well. "Eigenvector" is a horrible Frankenstein's monster of a word, grammatically speaking. And don't even get me started on "homomorphism" vs. "homeomorphism").

In fact, this phenomenon has led to English becoming almost mandatory for university-level technical education in many countries.

Emily
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In Hebrew (& in Israel) you always read equations in LTR.
There are no exceptions (not even inline equations, as one might expect).

RTL math doesn't exist here, so that's just a no, and it would be just as confusing and odd as it would in any other language or place.
So basically I'd say that no one will understand you, certainly won't bother to get accustomed to read it, even temporarily, and no teacher would so much as grade anything like that.

Note: I don't know how it is in the place Arkamis derived his answer from, but in Israel the reason isn't because of the ubiquitous existing text and material in LTR. The reason is just that it would feel very unnatural otherwise.

MasterMastic
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Just put in some parentheses, and then you don't have to worry about the LTR-vs-RTL issue. The expression $(a-b)-c$ means the same thing everywhere.

bubba
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    What about the expression $2 - 1$? That would certainly not be the same if read from either side. – Tobias Kildetoft Mar 05 '14 at 10:53
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    @Tobias -- well, maybe not. But $(1-2)$ would probably be unambiguous. But, I'm just guessing, really. Let's wait until we hear from someone who can read Arabic or Hebrew. At which point I might end up deleting my answer. – bubba Mar 05 '14 at 11:08
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    I wouldn't have thought "right to left" is about associativity: I would have thought it meant reading $(1-2)$ as starting with $2$ then subtracting $1$. –  Mar 05 '14 at 15:04
  • I was assuming that the parentheses would cause the "1-2" to be read as a "math block", and the parser (human or otherwise) would know that math blocks are supposed to be read in LTR order, regardless of the conventions of the enclosing text. – bubba Mar 06 '14 at 03:48