Functions preprocessor

• Extend keywords in AST2Expr
• Generate files
• Implementing new functions
• Integrating your own Java library with the WXF format

Add new identifiers in AST2Expr

To add new predefined constants or function symbols you have to extend the following String arrays in org.matheclipse.core.convert.AST2Expr

• UPPERCASE_SYMBOL_STRINGS - symbols which are exactly one uppercase constant or function
• DOLLAR_STRINGS - symbols starting with a '$' character
• SYMBOL_STRINGS - constant identifiers, which are not used as a function identifier
• FUNCTION_STRINGS - function identifiers

We can for example add a new user function MyFunction to the FUNCTION_STRINGS array.

Generate files

If the AST2Expr definitions have changed these two programs can generate new sources in the Eclipse console output:

• the FunctionIDGenerator.java program is used to generate the file org.matheclipse.core.expression.ID
• the BuiltinGenerator.java program is used to generate the predefined IBuiltInSymbol's in file org.matheclipse.core.expression.F

Implementing new functions

A new function is implemented in the package org.matheclipse.core.builtin

A typical "template" for an example built-in function MyFunction is implemented like this. The evaluation of MyFunction({a,b,c}) should return the first argument {a,b,c} if the first argument is a list.

package org.matheclipse.core.builtin;

import org.matheclipse.core.eval.EvalEngine;
import org.matheclipse.core.eval.exception.Validate;
import org.matheclipse.core.eval.interfaces.AbstractEvaluator;
import org.matheclipse.core.expression.F;
import org.matheclipse.core.interfaces.IAST;
import org.matheclipse.core.interfaces.IExpr;

public class UserFunctions {
	static {
		F.MyFunction.setEvaluator(new MyFunction());
	}

	private static class MyFunction extends AbstractEvaluator {

		@Override
		public IExpr evaluate(final IAST ast, EvalEngine engine) {
		   // test if only 1 argument is allowed:
			Validate.checkRange(ast, 2);
			if (ast.arg1().isList()) {
				return ast.arg1();
			}
			return F.NIL;
		}
	}

	private final static UserFunctions CONST = new UserFunctions();

	public static UserFunctions initialize() {
		return CONST;
	}

	private UserFunctions() {

	}

}

It must be initialized in the F.class static block:

...

	static {
		Thread INIT_THREAD = null;
...

			VectorAnalysisFunctions.initialize();
			QuantityFunctions.initialize();
			FinancialFunctions.initialize();
			WXFFunctions.initialize();
			WindowFunctions.initialize();
			UserFunctions.initialize();
...


	}	
...

Now the evaluation of MyFunction({a,b,c}) returns the first argument {a,b,c}. And the evaluation of MyFunction(test) returns unevaluated as MyFunction(test).

Integrating your own Java library with the WXF format

For creating a quick prototype which can use Symja functions to call your own library, you should consider implementing functions similar to the BinarySerialize, BinaryDeserialize functions with the WXF format: https://reference.wolfram.com/language/tutorial/WXFFormatDescription.html

The implementation whic is use in Symja can be found here:

• https://github.com/axkr/symja_android_library/blob/master/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/expression/WL.java
• https://github.com/axkr/symja_android_library/blob/master/symja_android_library/matheclipse-io/src/test/java/org/matheclipse/io/system/WXFTestCase.java