newRPL: symbolic numbers

12302014, 10:39 PM
Post: #24




RE: newRPL: symbolic numbers
Summing up this thread, here are some clear items:
To eliminate the approx/exact system mode, and to be able to emulate all its possible variations from within an expression, we need: a) Symbolic numbers b) Exact/approx numbers c) Exact/approx variables or expressions. d) Approx must "eat" exact. We explored two alternatives: 1) Exact/approx as a property of the numbers/variables: Can be seen as a flag or a "hint" for the numeric behavior of the number/variable for evaluation purposes only. 2) Approx as an operator: A fully defined prefix operator. Option 1): * The hint does not change the tree structure of the expression, so it's transparent to the CAS manipulations and rules. * Solvers can choose to use or ignore the hint when evaluating the expression. Option 2): * CAS needs to work with the operator explicitly. * The operator is transparent to nonCAS solvers when they evaluate the expression. For user interface, two proposed symbols: a) The trailing dot. b) The ~ prefix. Based on all the feedback, the best path seems to be Option 1) with a ~ prefix. A flag will also be included to use a trailing dot, for people familiar with TI, Mathematica, the HP50g and any other math software that already uses a trailing dot for approx. numbers. Now it's time to start coding all this. Thank you all for the feedback, I think we collectively came up with a very usable feature for newRPL. You should see it all working on the next demo release. Claudio. 

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