CAS command question

[Han]

(01-04-2017 11:19 AM)DrD Wrote:  

(01-04-2017 07:07 AM)parisse Wrote:  It may look like conter-intuitive, but once you know that, your programmer task will be easier, because you won't have to handle < or <= or binary - or /

Personally, I think that it is counter-intuitive,

Only when you are not aware of how the objects are stored internally. This would have been the same case with RPL.

Quote:and that it is not easier as a programmer.

Generally speaking, when you remove half of the cases to test, I would consider that easier. In terms of syntax, a<b is different from b>a. But mathematically, a<b is the same as b>a. By storing inequalities in a specific form (b>a rather than a<b), we reduce the syntax complexity.

Quote:My reasoning is that, intuitively, a programmer expects the left() command to always return the left side of an expression, ditto, the right().

Well, the documentation for these commands specify equalities or intervals. That they happen to not complain about other input should be the reason for complaint. Again, many examples of such behavior also exist in RPL, too (i.e. using commands to do things that were not originally considered). It just takes time to adjust to them.

Quote:For example, I recently created a routine to strip coefficients from an expression, needed for a coefficient matrix. A list of expressions, represented as string objects, was provided. The coeff() command was used, which required the expressions be separated into their left and right components. Counter-intuitively, this routine did not work when the inequality signs reversed. Worse than that, one might choose the wrong side command, during program testing, IF there were only "<" elements in the provided list used for input. This would typically be the case for optimality maximizing, as an example. The reason would be that the left() command would return the right side!

I would imagine that such code would necessarily have to detect whether the inequality was > or < and then branch accordingly. Wouldn't the complexity of your code increase as a result? If nothing else, you have more cases to handle, with the extra case(s) being very similar to existing cases.