2018-07-12 13:38 GMT+02:00 Frédéric van der Plancke <

[hidden email]>:

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> On 10/07/2018 23:56, Gregg Reynolds wrote:

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> On Tue, Jul 10, 2018, 4:44 PM Gregg Reynolds <

[hidden email]> wrote:

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>> (e.g. numbers in ltr scripts).

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> Correction: numbers in rtl scripts. Unicode says that numbers in e.g. Arabic are ltr. This is complete BS, but it is also a fact on the ground that cannot be fixed. Extra credit: estimate the cost of this very fundamental mistake.

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> I'm not sure it's a mistake, it may be a well-though design compromise.

>

> In arabic, the numbers are written in the same orientation as we do in european languages, because of a double inversion: from right to left, they first write the unit, then the 10s, then the 100s... the end result being that in both writing systems, the units go to the right and the heavier digits go to the left.

I once was an examiner in a mathematics competition in which some of

the competitors wrote in Arabic. The mathematical formulae were

written as Western mathematicians write them, and so were the numbers.

When I made a remark to this effect to my Algerian colleague, he

responded by asking me to add two ten-digit numbers that he had

written down. Naturally I started at the unit as I was taught in

primary school, and he stopped me right there. "Why do you start the

addition at the right, if you do everthing else from left to right?" I

replied "Because that's how the algorithm works." He then said: "But

it's our algorithm. An Arab mathematician invented it, and it starts

at the right because we write numbers that way."

He was right, you know!