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*From*: Hillel Wayne <hwayne@xxxxxxxxx>*Date*: Fri, 16 Apr 2021 14:10:54 -0500*References*: <22f7c06f-1774-4baf-98d6-32bdc244e0c7n@googlegroups.com>*User-agent*: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1

Hi Steve,

`\A` is "for all", so it will choose a value from S that
is ≥ all values. If you use `\E` instead, then it will
pick a value that is ≥ at least one value. Note that this includes
the value itself, so `\E y \in S: y <= x` is trivially
true for all values in the set.

H

On 4/16/2021 1:59 PM, Steve Ravet wrote:

I'm going through the examples at learntla.com and one asks to write an operator that finds the maximum value in a set. I did it using the SetReduce operator from somewhere else in the tutorial, but the given answer is simpler:--

Max(S) == CHOOSE x \in S : \A y \in S : y <= x

I can't quite "read" this. Since CHOOSE picks any value from the set where the condition is true, it seems like this would return a value from S that is larger than at least one other value, not larger than all other values. What makes it keep going to find the largest value?--

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**References**:**[tlaplus] How does this simple Max(set) implementation work?***From:*Steve Ravet

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