CAS command question

[DrD]

By "relation," I mean one side of an object is "related" to another.
By "operation," I mean how one side of an object is related to another.
Relationships are by means of less than, equal to, and greater than symbols.
(I'll add one other term for clarification for you):
By "expression" I mean each side of the relational operator.

With regard to our topic, I mean that there is a left side expression, a relation (symbol), and a right side expression. I mean, this forms a mathematical statement, in which these two items are analogous to the subject, and predicate; as in human language. Examples of what I mean are CAS commands that require "expressions."

Some CAS commands require access to the "expressions" of a mathematical sentence, predicated by some relationship, with an expression on the opposite side of that relationship.

Therefore when CAS makes an "evaluation," (and you know best what that is), I mean it is simply incorrect, and impolite, to hand a nice man like me, the predicate, when I ask for the subject of a statement. By "incorrect" I mean what Arno K has told you, "left is left, and right is right." A difficult concept, perhaps; but, nonetheless, fundamentally true. By "impolite" I mean it is rude of you to require the extra burden of correcting your error. By error, I mean sometimes you return the wrong expression. Now that I have explained what I mean, not to over use personal pronouns, I sure hope that I have explained, you get what I have explained, and I hope the explanation suffices.

If not, you may get better clarification if you replace (at least most of) the "I's" above, with "normal users." I mean I am normal, riiiiiiiight?

Quote:x<2 is an expression, left(x<2) is also an expression. The first one has '<' as rootnode, the second has 'left' as rootnode.

I see x<2 as a mathematical statement, a sentence, a relation. It relates the two "expressions", expression x, with the expression 2. The expression "x" is the subject, predicated by the relational operation, being less than the expression 2. By asserting that expression x is the subject, I mean, it is the expression being subjected to testing. Variable.

The expression "x" is on the left side of the relation, and the expression "2" is on the right side of that relational sentence. Returning the right side 2, when the left side x, is asked for is incorrect, and it's impolite.

Turning this back to you, some "normal users" might think of a tree's rootnode, for that term. Confusing, that you use the same term for '<' and 'left,' and most likely many other things. (Do rootnodes have left and right sides, too? It's as ambiguous as, well, returning right sides when left sides are expected).

[Maybe this trick will help explain]
If you tie a string, on your right hand finger, choice of finger optional, when you encounter a left() rootnode, STOP, think, "Does the "normal user" really want me to return the expression on the left hand side they asked for; or should I return the one on the right hand side, (you know, the hand with the string on it), and give them the finger, side?"

[GOOD NEWS!] There's room for compromise here, better handling of strings! Type casting: -changing object types- 'x<4' let's say, is a TYPE(8) and could be type cast to "x<4" let's call that a TYPE(2), then if both lhs() and rhs() operated on strings, (missing from the left() and right() commands), perhaps this would help(?)