CAS command question

[DrD]

(01-04-2017 03:06 PM)Han Wrote:  

(01-03-2017 11:33 AM)DrD Wrote:  2. If the intent IS to return the indicated side of an expression or interval, why was it necessary to first evaluate the expression?

3. If it is NOT necessary to first evaluate the expression, would you consider changing that behavior for the next release?

Regarding 2, this has always been the behavior. A literal (symbolic) expression requires quotation (single quotes). These are left unevaluated. Otherwise, it is "evaluated" as is normally done when entering commands on the command line. Simple example:

x:=t;
x+y // returns t+y
'x+y' // returns x+y

EDIT:

Quote:left('x+y<4'); ==> x+y
left(CAS("x+y<4")); ==> 4

The second case uses evaluation. left(CAS(" 'x+y<4' ")) will return x+y

Whenever I hear something corporate like, "we've always done it this way," etc., it's often a good time to re-visit the issue. Is there a better way? Minimize cost, maximize profit are typical measures. In this case, Arno K's very efficient point makes a better case for the cost of evaluation when using either of these two commands.

The second case is a necessary step to reveal the enclosed expression. It runs through a program without any distinction regarding the relation's symbols. That is a distinction WITH a difference, as compared to what happens when the expression is, itself, evaluated, resulting in the left/right handedness being exchanged.