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// Put the expression evaluator through its paces.

// Sample usage:

// $ java expr.Example '3.14159 * x^2' 0 4 1

// 0

// 3.14159

// 12.5664

// 28.2743

// 50.2654

// $ java expr.Example 'sin (pi/4 * x)' 0 4 1

// 0

// 0.707107

// 1

// 0.707107

// 1.22461e-16

// $ java expr.Example 'sin (pi/4 x)' 0 4 1

// I don't understand your formula "sin (pi/4 x)".

// I got as far as "sin (pi/4" and then saw "x".

// I expected ")" at that point, instead.

// An example of a formula I can parse is "sin (pi/4 + x)".

package expr;

/**

* A simple example of parsing and evaluating an expression.

public class Example {

public static void main(String[] args) {

Expr expr;

try {

expr = Parser.parse(args[0]);

} catch (SyntaxException e) {

System.err.println(e.explain());

return;

}

double low = Double.valueOf(args[1]).doubleValue();

double high = Double.valueOf(args[2]).doubleValue();

double step = Double.valueOf(args[3]).doubleValue();

Variable x = Variable.make("x");

for (double xval = low; xval <= high; xval += step) {

x.setValue(xval);

System.out.println(expr.value());

}