Re: Bug in SIMPLIFY? (hp 50g) Message #5 Posted by Nigel J Dowrick on 19 Aug 2009, 5:30 p.m., in response to message #4 by Luca
I've looked at this and I find it confusing too. I've defined the variables Q and M as you have. An expression containing only one of the two variables (e.g., Q^2+3) is unaffected by SIMPLIFY. However, an expression containing both (e.g., Q^2+3+M) gets converted into a number at once! I do not fully understand the reasoning behind this difference in behaviour. (Neither the "numeric" nor the "approx" mode settings are ticked.)
Of course, there are many "simplification" commands on the HP-50g: EXPAN, EXPAND, SEVAL, plus lots specific to trigonometry, powers, and logarithms. Give me a TI-89 for elementary algebra any day! Less powerful, no doubt, but it does what is expected.
To get around your problem (assuming you don't have a TI-89) you can create a subdirectory of HOME in which you store no variables. So long as you store no numeric variables in HOME either, you can simplify without risk of numeric substitutions if you change to this directory first. Not an ideal solution, and I can't help feeling that there ought to be another way around this, but it should work.
Nigel (still rather puzzled)
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