I'm back "discriminant" Help!

[TheOne]

Hello great folks of this great site,

As some of you know, I've been very busy studying networking and java. I have a serious question in java that's been bugging me all month:

What is the discriminant?

Can any one gives me a clear, down to earth definition of what this type is and how/when would I use it in a program?

the example code I have is below:

double b = Double.parseDouble(args[0]);
double c = Double.parseDouble(args[1]);
double discriminant = b*b - 4.0*c;
double d = Math.sqrt(discriminant);

I understand what the program is doing as far as printing the roots of the polynomials x^2 + bx + c
However, why couldn't they just use another double type variable at line 3 instead of discriminant?

wouldn't any other variable do the same operations of (b*b - 4.0*c)?

Thanks in advanced and happy new year to all

[clanmills]

Here's an explanation of the term "discriminant" which I obtained from a google search of "discriminant quadratic". (I haven't read this - however it looks OK).

http://www.mathwords.com/d/discriminant_quadratic.htm

The java code:

double discriminant = b*b - 4.0*c;
double d = Math.sqrt(discriminant);

could be written as:

double cheeseburgerwithfriesandashake = b*b - 4.0*c;
double d = Math.sqrt(cheeseburgerwithfriesandashake);

It would mean the same. The variable name chosen by the programmer is intended to help a (human) reader to understand the code and doesn't change the execution of the code.

I assume that you inherited this code from a programmer who (rightly) believes that the variable name "discriminant" is more meaningful than "cheeseburgerwithfriesandashake".

Of course it could be written as:

double d = Math.sqrt(b*b - 4.0*c);

This would totally short cut the need for a variable name. However the java function Math.sqrt requires a non negative number. I suspect when it 'bombs' with a negative number, it'll produce a message such as 'b*b -4.0c' cannot be negative. The programmer preferred the message 'discriminant' cannot be negative.

Of course you can modify the java 'bomb' experience with try ... catch ... however that's another matter about which you'll have to learn.

Happy New Year to you. Best Wishes for 2010.

Robin