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Re: Implementation of boolean types.

From: Mikito Harakiri <mikharakiri_nospaum_at_yahoo.com>
Date: 17 Jul 2005 11:13:15 -0700

Drago Ganic wrote:
> Marshall,
> Symbolic programming is a good solution for null values. See these trivial
> evaluations:
> y = 1+x --> 1+x
> y - x --> 1
>
> z = (1,1,x) --> 2 + x
> z - x -->2

This is a great idea.

> Remember elementary algebra: We learned how to calculate with unknowns in
> elementary school :-)) But CS forgot to build it in computing. I strongly
> believe CAS [Computer Algebra Systems] are needed for solving the null
> problem.
>
> The practical problem is that expressions with "unknown variables" (symbols)
> tend to get really big
> (e.g. z + y --> (2 + x) + (1+x) -->3 + 2x).

The expression can be collapsed. Say there are only 3 known values of Bonus in the Emp table (out of 10). Then

totalBonus = 1000 + x1 + x2 + 2000 + x3 + 3000 + x5 + x6 + x7 = = 6000 + (x1 + x2 + x3 + x5 + x6 + x7) = 6000 + y

An implicit rule is that expressions involving variables can be renamed to other variable. Received on Sun Jul 17 2005 - 13:13:15 CDT

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