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1
3 package org.jmock.examples.calculator;
4
5 import java.io.IOException  ;
6
7
8
21 public class InfixParser implements Parser
22 {
23 private ExpressionFactory factory;
24
25 public InfixParser() {
26 this(new SimpleExpressionFactory());
27 }
28
29 public InfixParser( ExpressionFactory factory ) {
30 this.factory = factory;
31 }
32
33 public Expression parse( String expressionString ) throws ParseException {
34 Lexer lexer = new Lexer(expressionString);
35 try {
36 return parseExpression(lexer);
37 }
38 catch (IOException ex) {
39 throw new ParseException("I/O error when parsing expression", ex);
40 }
41 }
42
43 private Expression parseExpression( Lexer lexer )
44 throws ParseException, IOException {
45 return parseAddExpr(lexer);
46 }
47
48 private Expression parseAddExpr( Lexer lexer )
49 throws ParseException, IOException {
50 Expression left = parseMulExpr(lexer);
51
52 for (; ;) {
53 Token token = lexer.nextToken();
54
55 switch (token.getType()) {
56 case Token.ADD:
57 left = factory.newAddition(left, parseAddExpr(lexer));
58 break;
59 case Token.SUBTRACT:
60 left = factory.newSubtraction(left, parseAddExpr(lexer));
61 break;
62 default:
63 lexer.pushBack(token);
64 return left;
65 }
66 }
67 }
68
69 private Expression parseMulExpr( Lexer lexer )
70 throws ParseException, IOException {
71 Expression left = parsePowExpr(lexer);
72
73 for (; ;) {
74 Token token = lexer.nextToken();
75
76 switch (token.getType()) {
77 case Token.MULTIPLY:
78 left = factory.newMultiplication(left, parseMulExpr(lexer));
79 break;
80 case Token.DIVIDE:
81 left = factory.newDivision(left, parseMulExpr(lexer));
82 break;
83 default:
84 lexer.pushBack(token);
85 return left;
86 }
87 }
88 }
89
90 private Expression parsePowExpr( Lexer lexer )
91 throws ParseException, IOException {
92 Expression left = parseValExpr(lexer);
93
94 for (; ;) {
95 Token token = lexer.nextToken();
96
97 switch (token.getType()) {
98 case Token.POWER:
99 left = factory.newPower(left, parsePowExpr(lexer));
100 break;
101 default:
102 lexer.pushBack(token);
103 return left;
104 }
105 }
106 }
107
108 private Expression parseValExpr( Lexer lexer )
109 throws ParseException, IOException {
110 Token token = lexer.nextToken();
111
112 switch (token.getType()) {
113 case Token.NUMBER:
114 return factory.newLiteral(parseValue(token.getValue()));
115
116 case Token.IDENTIFIER:
117 return factory.newVariableReference(token.getValue());
118
119 case Token.PAREN_OPEN:
120 {
121 Expression result = parseExpression(lexer);
122
123 if (lexer.nextToken().getType() != Token.PAREN_CLOSE) {
124 throw new ParseException("closing parenthesis missing");
125 }
126
127 return result;
128 }
129
130 case Token.END:
131 throw new ParseException("unexpected end of input");
132
133 default:
134 throw new ParseException("unexpected token \"" + token.getValue() + "\"");
135 }
136 }
137
138 public double parseValue( String valueString )
139 throws ParseException {
140 try {
141 return Double.parseDouble(valueString);
142 }
143 catch (NumberFormatException ex) {
144 throw new ParseException("invalid number literal \"" + valueString + "\"");
145 }
146 }
147 }
148
149 |
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