HP-19Bii variables and plotting

[Don Shepherd]

(11-18-2014 07:56 AM)x34 Wrote:  I wonder why the calc does have such cruel restrictions?

Well, considering the 17b and 19b came out in January of 1988, almost 27 years ago, I've always considered it amazing that they had the "programming" features like sigma and IF() at all. If an equation solver is meant to just solve equations, those features would not be needed. In fact, I don't know of any other equation solver that has them. Yes, I would absolutely love the ability to write to a sum list in a solver equation. A few years ago I even found one of the original 17b developers (Paul McClellan) and contacted him about the possible existence of a hidden command to write to a sum list; if there is such a command, he didn't know about it. Having the ability to write to a sum list in a solver equation would open up the solver to many additional programming possibilities. But the 17b is still an extraordinary machine.