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diff --git a/core/src/de/congrace/exp4j/FunctionToken.java b/core/src/de/congrace/exp4j/FunctionToken.java
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+++ b/core/src/de/congrace/exp4j/FunctionToken.java
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+/*
+Copyright 2011 frank asseg
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+ */
+package de.congrace.exp4j;
+
+import java.util.Stack;
+
+/**
+ * A {@link Token} for functions
+ * 
+ * @author fas@congrace.de
+ * 
+ */
+class FunctionToken extends CalculationToken {
+	/**
+	 * the functionNames that can be used in an expression
+	 * 
+	 * @author ruckus
+	 * 
+	 */
+	enum Function {
+		ABS, ACOS, ASIN, ATAN, CBRT, CEIL, COS, COSH, EXP, EXPM1, FLOOR, ROUND, RANDOM, LOG, SIN, SINH, SQRT, TAN, TANH, LOG10
+	}
+
+	private Function function;
+
+	/**
+	 * construct a new {@link FunctionToken}
+	 * 
+	 * @param value
+	 *            the name of the function
+	 * @throws UnknownFunctionException
+	 *             if an unknown function name is encountered
+	 */
+	FunctionToken(String value) throws UnknownFunctionException {
+		super(value);
+		try {
+			function = Function.valueOf(value.toUpperCase());
+		} catch (IllegalArgumentException e) {
+			throw new UnknownFunctionException(value);
+		}
+		if (function == null) {
+			throw new UnknownFunctionException(value);
+		}
+	}
+
+	/**
+	 * apply a function to a variable
+	 * 
+	 * @param x
+	 *            the value the function should be applied to
+	 * @return the result of the function
+	 */
+	public Variable applyFunction(Variable var) {
+		
+		// The names here are strictly unused, but are useful for debugging
+		String name = function.name() + " result (#"+var.hashCode()+"), ";
+		
+		switch (var.getPrimary()) {
+			case DOUBLE:
+				name = "double "+name;
+				double x = var.getDoubleValue();
+				return new Variable(name, applyFunction(x) );	
+			
+			case ARRAY:
+				name = "array "+name;
+				double[] input = var.getArrayValue();
+				double[] result = new double[input.length];
+				for (int i = 0; i < input.length; i++){
+					result[i] = applyFunction(input[i]);
+				}
+				return new Variable(name, result);
+			
+			default:
+				return new Variable("Invalid");
+		}
+	}
+	
+	/*
+	 * The actual function application on a double
+	 */
+	private double applyFunction(double x){
+		switch (function) {
+		case ABS:
+			return Math.abs(x);
+		case ACOS:
+			return Math.acos(x);
+		case ASIN:
+			return Math.asin(x);
+		case ATAN:
+			return Math.atan(x);
+		case CBRT:
+			return Math.cbrt(x);
+		case CEIL:
+			return Math.ceil(x);
+		case COS:
+			return Math.cos(x);
+		case COSH:
+			return Math.cosh(x);
+		case EXP:
+			return Math.exp(x);
+		case EXPM1:
+			return Math.expm1(x);
+		case FLOOR:
+			return Math.floor(x);
+		case ROUND:
+			return Math.round(x);
+		case RANDOM:
+			return Math.random()*x;
+		case LOG:
+			return Math.log(x);
+		case LOG10:
+			return Math.log10(x);
+		case SIN:
+			return Math.sin(x);
+		case SINH:
+			return Math.sinh(x);
+		case SQRT:
+			return Math.sqrt(x);
+		case TAN:
+			return Math.tan(x);
+		case TANH:
+			return Math.tanh(x);
+		default:
+			return Double.NaN; // should not happen ;)
+		}
+	}
+
+	/**
+	 * 
+	 * get the {@link Function}
+	 * 
+	 * @return the correspoding {@link Function}
+	 */
+	Function getFunction() {
+		return function;
+	}
+
+	@Override
+	void mutateStackForCalculation(Stack<Variable> stack, VariableSet variableValues) {
+		stack.push(this.applyFunction(stack.pop()));
+	}
+
+	@Override
+	void mutateStackForInfixTranslation(Stack<Token> operatorStack, StringBuilder output) {
+		operatorStack.push(this);
+	}
+}