Hi Johannes,

(cog-number (Number 3))

Amen B.

On Friday, December 28, 2018 at 2:57:27 AM UTC+8, Johannes Castner wrote:
>
> Hi Nil, 
>
> Is there a way to get the value from a NumberNode?  In other words, can I 
> get the 4 out of (NumberNode 4)?  I need to do some other, quite general 
> intermediate calculations and then produce another NumberNode; how do I 
> best do that?
>
> Johannes
>
>>
>> There are different ways to do that, and they depend on what you 
>> intend to do with the knowledge. One way would be to use value 
>>
>> https://wiki.opencog.org/w/Value 
>>
>> for instance to attach a score of 3 to John, you'd say 
>>
>> ``` 
>> (define john (Concept "John")) 
>> (define score (Concept "score")) 
>> (cog-set-value! john score (Number 3)) 
>> ``` 
>>
>> then you may ask John's score with 
>> ``` 
>> (cog-value john score) 
>> ``` 
>> which will return 3. 
>>
>> Later on you may update John's score with 
>> ``` 
>> (cog-set-value! john score (Number 4)) 
>> ``` 
>>
>> And 
>> ``` 
>> (cog-value john score) 
>> ``` 
>> which will return 4. 
>>
>> The problem with that (and with mutability in general) is that you 
>> lose information. So for instance you won't be able to use reasoning 
>> or specialized forms thereof like pattern mining to analyze the 
>> evolution of your data. For that you need to keep track of these 
>> updates. One way could be to use AtTimeLink, so for instance you way 
>> write that at 10pm John had a score of 3 
>>
>> AtTimeLink 
>>    Evaluation 
>>      Predicate "score-of" 
>>      List 
>>        (Concept "John") 
>>        (Number 3) 
>>    TimeNode "10pm" 
>>
>> but at 11pm he had a score of 4 
>>
>> AtTimeLink 
>>    Evaluation 
>>      Predicate "score-of" 
>>      List 
>>        (Concept "John") 
>>        (Number 4) 
>>    TimeNode "10pm" 
>>
>> Etc... There are many ways to represent knowledge. 
>>
>

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