Absolute value: sometimes CAS is very clever, sometimes not!

[ijabbott]

(09-08-2018 03:28 PM)compsystems Wrote:  

(09-08-2018 10:43 AM)ijabbott Wrote:  Back to compsystem's point, why does 'x ≠ -1' get simplified to a boolean 'true' if x is unknown?

(09-08-2018 10:52 AM)parisse Wrote:  Because x (identifier) is different from 1 (integer), like for == which does not mean "mathematically equivalent".

And with what purpose the operadopr = acts as ==, if there is a command (==) or evalb() for that purpose, also for ≠

'==' and '≠' seem most mostly in the same class as each other, although x≠1 →true, but x==1→0 (rather than 'false'). '=' seems to be for equalities as in equating two sides of an equation and seems to be in the same class as '<', '≤', '>', and '≥' as far as the CAS is concerned. What is missing is a "not equal to" operator in the same class as '<', '>'. etc.

Quote:I think that the operator =, ≠, should not operate as a comparator, this affects the logic of the algorithms, so I suggest a cas flag for these operators if they find symbols do not assume the comparison.

I'm not a big fan of using special flags, but agree that something is needed.