21 Jun
2011
21 Jun
'11
11:30 a.m.
I suppose a calculator with infix entry wouldn't
be so bad if it
would store the entire entry until the = key is pressed, then
evaluate it observing rules of operator precedence.
But none AFAIK do, so an infix calculator really isn't.
Eh? A lot do, going back to the HP9830 (and I think the HP9820, but it's
been a few months since I used that machine). You can type in a long
expression and then evalulate it. You can also recall the expression,
change it and re-evalulate. Yes, these machines are almost 40 years old
now...
Many modern calculators from Casio, TI, Sharp, etc let you do much the
same thing. The HP49/50 series let you either work in algebraic mode
(where they behave like a TI/Casio roughly) or in RPN mode. In the latter
mode you can push an algebraic (infix) expression onto the stack and
evaluate it, or manipulate it.
Perhaps one of the nicest pure infix machines was the HP71B. That has a
'calc' mode where you cna type in an expression and evlauate it, recall
if for editing, etc. But it also has the feature that as soon as a
sub-expression cna be evaluated, it will do so. For example :
If you type 2*3, it remains as that on the display. If you then type +,
the dispaly changes to 6+ (since + hasa lower priortiy than *, the
multiplication cna be evaulated at that point, so that's what the machine
does). It's _almost_ as nice as RPN in that is shows you intermediate
answers too. But I still prefer RPN.
-tony