How to make a Java program that recognises a function of two variables...

Question

How to make a Java program that recognises a function of two variables to assign values to that?
First I will give an example and then do the question.
Ex1.
We have any function, eg.y = x ^ 2 + 1 (read 'y' equals 'x' high to the square), a function of the second degree.
To build the graph of this function attach values to 'x' to find the values of 'y'
And thus mount the pair ordered (x, y) which represents a point on the Cartesian plane.
Assigning values to 'x' 'we can build up a table that gives us the pairs ordered:
We can use any numbers, but arfer interval [-3.3]
X | y = x ^ 2 + 1
-3 | Y = (-3) ^ 2 +1 = 10
-2 | Y = (-2) ^ 2 +1 = 5
-1 | Y = (-1) ^ 2 +1 = 2
0 | y = (0) ^ 2 +1 = 1
1 | y = (1) ^ 2 +1 = 2
2 | y = (2) ^ 2 +1 = 5
3 | y = (3) ^ 2 +1 = 10
We then ordered the pairs:
(-3.10), (-2.5); (-1.2), (0,1), (1,2), (2,5), (3,10)
Tabem that can be represented by a table:
X | y
-3 | Y = 10
-2 | Y = 5
-1 | Y = 2
0 | y = 1
1 | y = 2
2 | y = 5
3 | y = 10
Now I begin to explain my doubts.
See this program:
Ex2
* To change this template, choose Tools | Templates
* And open the template in the editor.
Encontrando_o_valor_de_y package;
* @ Author des Soldat Gottes
Import javax.swing.JOptionPane;
Public class (Main
* @ Param args the command line arguments
Public static void main (String [] args) (
Int x, y;
String x1;
X1 = JOptionPane.showInputDialog ( "We have the function y = x + 1 \ n" +
"Assign a value for 'x',"); / / receives a value for the function y = x + 1
X = Integer.parseInt (x1); / / tranforma String in int
Y = x + 1; / / receives the value of 'x' and calculates' y '
JOptionPane.showMessageDialog (null, "The value of 'y' is: \ t \ t" + y);
/ / Displays the value of 'y'
System.exit (0);
We see that the program receives above a value for 'x' and replaces the function contained in the program, y = x + 1, and so is the value of the variable 'y'.
In: x1 = JOptionPane.showInputDialog ( "We have the function y = x + 1 \ n" +
"Assign a value for 'x',");
The entry is a number and that number is assigned aa ja existing function in the (y = x + 1).
The question is: would it be possible to come to a function?
Ex: the program ask: DIGITE THE FUNCTION?
The USUARIO DIGITARIA A FUNCTION ANY, TYPE: y = x ^ 2 +1
The program would recognize the function and give numerical values to that function as Ex1, at the beginning of this text.
And then to find the values of the x and y launch a table.
It would be possible that?
By invez of entering with a number so that the program sustitua a function ja existing as Ex2, seen above, entering with a function quaquer (type: y = x ^ 2 +1) for the program atribuisse values to that function and then create a table of values as Ex1.
I hope it has been easier to understand my doubts now.
Thank you for your attention!
God bless!

Answer 1

rafaelmenezes wrote:
Thanks for the explanation, could understand what fly said.
But as it applied to a program?
How to create a program that recognizes that the entry coefficients?Are you asking about how to parse out the coefficients from the string "3x^4 + 4x^3 - 8x^2 + 5x^1 + 2x^0"? If you define the format to strictly follow that example, this should get you started:
Strip out the spaces
Split the String on "x^"
That should give you [3, 4+4, 3-8, 2+5, 1+2, 0]
Split each resulting String on "+ | -", preserving the operator as a token so you can apply the correct sign to the coeff.
That should leave you with [3, 4, +, 4, 3, -, 8, 2, +, 5, 1, +, 2, 0]. Every other number is a coeff, the rest are the degrees.
You can strip out the +, since those coeffs are already positive, and strip out the - after negating the following number. This is all assuming that you have to write this yourself. There is no doubt already a library or 5 out there that does this for you.