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Java usage

Ax Kr edited this page Aug 31, 2019 · 10 revisions

How to use Symja as a Java library

Here is an annotated Java usage Example:

package org.matheclipse.core.examples;

import org.matheclipse.core.eval.ExprEvaluator;
import org.matheclipse.core.expression.F;
import org.matheclipse.core.interfaces.IAST;
import org.matheclipse.core.interfaces.IExpr;
import org.matheclipse.core.interfaces.ISymbol;
import org.matheclipse.parser.client.SyntaxError;
import org.matheclipse.parser.client.math.MathException;

public class Example {
	public static void main(String[] args) {
		try {
			ExprEvaluator util = new ExprEvaluator(false, 100);

The method toJavaForm converts an expression to the internal Java form.

Note: single character identifiers are case sensitive (the D function identifier must be written as upper case character)

			String javaForm = util.toJavaForm("D(sin(x)*cos(x),x)");

The following line will print: D(Times(Sin(x),Cos(x)),x)

			System.out.println("Out[1]: " + javaForm.toString());

Use the Java form to create an expression with F.* static methods:

			ISymbol x = F.Dummy("x");
			IAST function = F.D(F.Times(F.Sin(x), F.Cos(x)), x);
			IExpr result = util.eval(function);

The following line will print: Cos(x)^2-Sin(x)^2

			System.out.println("Out[2]: " + result.toString());
			result = util.eval("diff(sin(x)*cos(x),x)");

The following line will print the same result: Cos(x)^2-Sin(x)^2, because diff is an alias for the D function.

			System.out.println("Out[3]: " + result.toString());

Evaluate the last result (% contains the last answer)

			result = util.eval("%+cos(x)^2");

The following line will print: 2*Cos(x)^2-Sin(x)^2

			System.out.println("Out[4]: " + result.toString());

Evaluate an Integrate() expression.

			result = util.eval("integrate(sin(x)^5,x)");

The following line will print: 2/3*Cos(x)^3-1/5*Cos(x)^5-Cos(x)

			System.out.println("Out[5]: " + result.toString());

Set the value of a variable a to 10.

			result = util.eval("a=10");

Print 10.

			System.out.println("Out[6]: " + result.toString());

Do a calculation with variable a:

			result = util.eval("a*3+b");

Print: 30+b

			System.out.println("Out[7]: " + result.toString());

Do a calculation in "numeric mode" with the N() function.

Note: single character identifiers are case sensistive (the N function identifier must be written as upper case character)

			result = util.eval("N(sinh(5))");

Print: 74.20321057778875

			System.out.println("Out[8]: " + result.toString());

Define a function with a recursive factorial function definition.

Note: fac(0) is the stop condition for the recursion.

			result = util.eval("fac(x_IntegerQ):=x*fac(x-1);fac(0)=1");
			// now calculate factorial of 10:
			result = util.eval("fac(10)");

Print: 3628800.

			System.out.println("Out[9]: " + result.toString());

		} catch (SyntaxError e) {

You can catch Symja parser errors with the SyntaxError exception here:

			System.out.println(e.getMessage());
		} catch (MathException me) { 
			System.out.println(me.getMessage());
		} catch (final Exception ex) {
			System.out.println(ex.getMessage());
		} catch (final StackOverflowError soe) {
			System.out.println(soe.getMessage());
		} catch (final OutOfMemoryError oome) {
			System.out.println(oome.getMessage());
		}
	}
}
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