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I want to describe the following set...

{ "Person1", "Person2", "Person3"... }

... where the number is from 1.. 100.

How do I do this using mathematical set description?

Asaf Karagila
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3 Answers3

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My solution: $$\{\text{"Person"} + \operatorname{str}(k) : 1 \le k \le 100 \land k \in \mathbb N\}$$

whereby $+$ is the concatenation of strings and $\operatorname{str}(\cdot)$ is a function converting a number into its decimal string representation. strings can be mathematically described as finite lists of characters (which is also done in many programming languages).

The advantage: The above statement can be tranfered to many programming languages. For example in python you can write:

set([ "Person" + str(k+1) for k in range(0,100) ])
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You can say this: We have $26$ symbols of the english alphabet and $10$ symbols $\{0,1,...,9\}$ that can produce all the numbers. Now your set can be described as $S=\{xn:x=Person$ and $n\in [1,100]\}\subset \mathbb F_{36}$ the free group with $36$ generators.

Haha
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That set is not a mathematical object. As far as I know, math has not a standard notation to describe such thing. Computer languages or pseudocode may work better for that.

ajotatxe
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    Could you possibly give the definition of "mathematical object" that you are using? I'm pretty sure that's also nonstandard. – Matt Samuel Jan 30 '15 at 16:42
  • I have not a definition for "mathematical object", but surely persons are not... – ajotatxe Jan 30 '15 at 16:45
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    Certainly persons can be. So can my toaster. Even without being so avant garde, though, those aren't people, they are strings. Sequences of characters. – Matt Samuel Jan 30 '15 at 16:46