[X4U] Tiger's Calculator.app no longer does percentages?

[Andrew Swanson]

I will dispute what "15%" means. 15% is 0.15.
On the other hand, "15% of" means 0.15 times, but "15%" alone means  
15/100.

However, the dispute here really comes down to whether "%" is a  
binary operator (percent of), unary operator (percent) or something  
else (percent markup, perhaps).

If "%" is a binary (percent of) operator acting on two numbers, then  
the key sequence 15%28.00= should give a result like 4.20, while the  
sequence 28.00+15%= is ambiguous because there should be a number  
after the "%" in the sequence. This does not mean that calculator  
manufacturers have not chosen various ways to resolve the ambiguity -  
none of them strictly correct (I contend that the mathematically  
correct result is an error message. This is not a result users would  
find useful, so manufacturers have tried a variety of alternatives.)

If "%" (percent) acts on one number the correct answer is definitely  
15%=0.15.

If "%" is something else, there is no telling how it will behave  
without testing what the manufacturer decided. It is perfectly  
reasonable to have a "markup" key that calculates a percentage of a  
previously displayed result.

I agree that it is annoying if a manufacturer changes from one  
interpretation of the operator to another between revisions of a  
product.

Most calculators I deal with, by the way, have lots of keys, none of  
which is "%".

    Andy

BTW: Apple's scientific calculator correctly handles the cases asked  
about. Fortunately, Apple's calculator, like most scientific  
calculators, has separate unary and binary "-" functions - unlike the  
keyboard.

The semi-ambiguous first case -2^2 is handled correctly as (-2)^2=4  
if you use the unary "-" function, while -2^2 is also correctly dealt  
with as 0-2^2=-4. and so forth...