+/*
+ 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.Set;
+import java.util.Stack;
+
+/**
+ * Class for calculating values from a RPN postfix expression.<br/>
+ * The default way to create a new instance of {@link PostfixExpression} is by
+ * using the static factory method fromInfix()
+ *
+ * @author fas@congrace.de
+ */
+public final class PostfixExpression extends AbstractExpression implements Calculable {
+
+ private VariableSet variables = new VariableSet();
+
+ /**
+ * Factory method for creating {@link PostfixExpression}s from human
+ * readable infix expressions
+ *
+ * @param expression
+ * the infix expression to be used
+ * @return an equivalent {@link PostfixExpression}
+ * @throws UnparsableExpressionException
+ * if the expression was invalid
+ * @throws UnknownFunctionException
+ * if an unknown function has been used
+ * @deprecated please use {@link ExpressionBuilder} API
+ */
+ @Deprecated
+ public static PostfixExpression fromInfix(String expression) throws UnparsableExpressionException, UnknownFunctionException {
+ return fromInfix(expression, null);
+ }
+
+ /**
+ * Factory method for creating {@link PostfixExpression}s from human
+ * readable infix expressions
+ *
+ * @param expression
+ * the infix expression to be used
+ * @param customFunctions
+ * the CustomFunction implementations used
+ * @return an equivalent {@link PostfixExpression}
+ * @throws UnparsableExpressionException
+ * if the expression was invalid
+ * @throws UnknownFunctionException
+ * if an unknown function has been used
+ * @deprecated please use {@link ExpressionBuilder}
+ */
+ @Deprecated
+ public static PostfixExpression fromInfix(String expression, Set<CustomFunction> customFunctions) throws UnparsableExpressionException,
+ UnknownFunctionException {
+ String[] variableStrings = null;
+ int posStart, posEnd;
+ if ((posStart = expression.indexOf('=')) > 0) {
+ String functionDef = expression.substring(0, posStart);
+ expression = expression.substring(posStart + 1);
+ if ((posStart = functionDef.indexOf('(')) > 0 && (posEnd = functionDef.indexOf(')')) > 0) {
+ variableStrings = functionDef.substring(posStart + 1, posEnd).split(",");
+ }
+ }
+ return new PostfixExpression(InfixTranslator.toPostfixExpression(expression, variableStrings, customFunctions), variableStrings, customFunctions);
+ }
+
+ /**
+ * Construct a new simple {@link PostfixExpression}
+ *
+ * @param expression
+ * the postfix expression to be calculated
+ * @param variableNames
+ * the variable names in the expression
+ * @param customFunctions
+ * the CustomFunction implementations used
+ * @throws UnparsableExpressionException
+ * when expression is invalid
+ * @throws UnknownFunctionException
+ * when an unknown function has been used
+ */
+ private PostfixExpression(String expression, String[] variableStrings, Set<CustomFunction> customFunctions) throws UnparsableExpressionException,
+ UnknownFunctionException {
+ super(expression, new Tokenizer(variableStrings, customFunctions).tokenize(expression), variableStrings);
+ }
+
+ /**
+ * delegate the calculation of a simple expression
+ */
+ public Variable calculate() throws IllegalArgumentException {
+
+ final Stack<Variable> stack = new Stack<Variable>();
+ for (final Token t : getTokens()) {
+ ((CalculationToken) t).mutateStackForCalculation(stack, variables);
+ }
+ return stack.pop();
+
+ }
+
+ public void setVariable(Variable value) {
+ variables.add(value);
+ }
+}