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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 com.github.cgdon.jexpr.example;

import com.github.cgdon.jexpr.core.Parser;
import com.github.cgdon.jexpr.core.expr.Variable;
import com.github.cgdon.jexpr.core.Expr;
import com.github.cgdon.jexpr.core.SyntaxException;

/**
 * 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());
    }
  }
}