10-25-2015, 12:31 PM
Post: #95
 Claudio L. Senior Member Posts: 1,699 Joined: Dec 2013
(10-25-2015 11:31 AM)Han Wrote:  While I think the "dot" notation is nice for immediate evaluation, it really seems to be contrary to the whole notion of RPN.

'X^2+Y' 1 + --> 'X' SQ 'Y' + 1 +
'X^2+Y.' 1 + --> 'X' SQ Y + 1 +
This is exactly right, but I fail to see why it's contrary to RPN (??). All you are telling the machine is that you want the value of Y replaced ASAP.
I think for instance of a quadratic solver.
You have the generic equation:
'a.*X^2+b.*X+c.' stored somewhere

Then the user defines 'a', 'b' and 'c' to his liking.
Next time you operate on that expression, all 3 values will be immediately replaced, but not X, so you can display the final equation even if X has a value. Doing EVAL would also replace the X if it has any value. This way you control what gets replaced in the expression.
Currently, you'd need to make sure X doesn't exist in current or higher directories to get the equation.

(10-25-2015 11:31 AM)Han Wrote:  But even with the feature, I am not sure it would be used as described. If I wanted immediate substitution, I imagine that I would still end up double checking the value of Y prior to having the calculator actually include it into a formula. So a quick RCL of the contents of Y would most likely occur -- and at this point I may as well just build my formula with the Y value already on the stack.

Ah, but you are thinking interactively only. The dot in the expression is most useful when executed inside a program, since the mere presence of the symbolic in the runstream would trigger the replacement. Without the dot, you'd have to break down the expression in the program so you can evaluate the different parts and then reconstruct the symbolic.

Think of my example above:
Currently:
<< a 'X^2' * b 'X' * + c + >>
Proposed:
<< 'a.*X^2+b.*X+c.' >>

They produce the same result.
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