package org.matheclipse.core.builtin.function;

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

/**
 */
public class First extends AbstractCoreFunctionEvaluator {

	public First() {
	}

	@Override
	public IExpr evaluate(final IAST ast) {
		Validate.checkSize(ast, 2);
		IExpr arg1 = F.eval(ast.arg1());
		if (!arg1.isAST()) {
			return null;
		}
		final IAST sublist = (IAST) arg1;

		if (sublist.size() > 1) {
			return sublist.arg1();
		}

		return null;
	}
}