package org.matheclipse.core.reflection.system;

import org.matheclipse.core.eval.exception.Validate;
import org.matheclipse.core.eval.interfaces.AbstractFunctionEvaluator;
import org.matheclipse.core.interfaces.IAST;
import org.matheclipse.core.interfaces.IExpr;
import org.matheclipse.core.interfaces.ISymbol;

/**
 * Get the default value for a symbol (i.e. 1 is the default value for Times, 0 is the
 * default value for Plus).
 */
public class Default extends AbstractFunctionEvaluator {

	public Default() {
	}

	@Override
	public IExpr evaluate(final IAST ast) {
		Validate.checkRange(ast, 2, 4);
		ISymbol symbol = Validate.checkSymbolType(ast, 1);

		if (ast.size() > 2) {
			int pos = Validate.checkIntType(ast, 2);
			return symbol.getDefaultValue(pos);
		} else {
			return symbol.getDefaultValue();
		}
	}

}