lexan/syntax.py at master · kroschenko/lexan · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172

class SyntaxisAnalyzer:

    def __init__(self, lexeme_list, table):
        self.lexeme_list = lexeme_list
        self.index = 0
        self.lexem = None
        self.table = table
        self.error_code = 0

    def extract_next_lexeme(self):
        self.lexem = self.lexeme_list.pop()

    def get_next_lexeme(self):
        return self.lexeme_list[-1]

    def eq(self, str):
        if self.table[self.lexem[0]-1][self.lexem[1]] == str:
            return True
        else:
            return False

    def error(self, index):
        self.error_code = index
        if index == 1:
            raise Exception("Missing ':'")
        elif index == 2:
            raise Exception("Missing type of variable")
        elif index == 3:
            raise Exception("Missing ';'")
        elif index == 4:
            raise Exception("Missing begin keyword")
        elif index == 5:
            raise Exception("Missing end keyword")
        elif index == 6:
            raise Exception("Missing ')'")
        elif index == 7:
            raise Exception("Missing ']'")

    def id(self):
        return self.lexem[0] == 4

    def num(self):
        return self.lexem[0] == 3

    def identifier(self):
        return self.lexem[0] == 4

    def number(self):
        pass

    def description(self):
        while self.identifier():
            self.extract_next_lexeme()
            if self.eq(','):
                self.extract_next_lexeme()
        if not self.eq(':'):
            self.error(1)
        else:
            self.extract_next_lexeme()
            if not (self.eq('integer') or self.eq('real')):
                self.error(2)
            else:
                self.extract_next_lexeme()
                if not self.eq(';'):
                    self.error(3)

    def begin(self):
        if not self.eq('begin'):
            self.error(4)
        else:
            self.extract_next_lexeme()

    def operators(self):
        while self.assign():
            pass

    def operator(self):
        pass

    def end(self):
        if not self.eq('end'):
            self.error(5)
        else:
            self.extract_next_lexeme()

    def program(self):
        if self.eq('program'):
            self.extract_next_lexeme()
            self.identifier()
            self.extract_next_lexeme()
            if not self.eq(';'):
                self.error(3)
            else:
                self.extract_next_lexeme()
        if self.eq('var'):
            self.extract_next_lexeme()
            self.description()
            self.extract_next_lexeme()
        self.begin()
        self.operators()
        self.end()

    def assign(self):
        self.variable()
        self.extract_next_lexeme()
        if self.eq(':='):
            self.extract_next_lexeme()
            self.expression()
        else:
            return False
        return True

    def expression(self):
        self.term()
        self.extract_next_lexeme()
        while self.eq('+') or self.eq('-'):
            self.extract_next_lexeme()
            self.term()
        return True

    def term(self):
        self.primary()
        while self.eq('*') or self.eq('/'):
            self.extract_next_lexeme()
            self.primary()
        return True

    def primary(self):
        if self.id():
            self.variable()
        elif self.num():
            self.number()
        elif self.eq('('):
            self.extract_next_lexeme()
            self.expression()
            if self.eq(')'):
                self.extract_next_lexeme()
            else:
                self.error(6)
        else:
            return False
        return True

    def variable(self):
        self.identifier()
        if self.eq('['):
            self.extract_next_lexeme()
            self.subList()
            if self.eq(']'):
                self.extract_next_lexeme()
            else:
                self.error(7)

    def subList(self):
        self.expression()
        while self.eq(','):
            self.extract_next_lexeme()
            self.expression()

    def run_analysis(self):
        try:
            self.index = 0
            self.extract_next_lexeme()
            self.program()
        except Exception as e:
            print("Error: " + str(e))
        finally:
            if self.error_code == 0:
                print('Syntax analysis finished successfully!')
            else:
                print('Syntax analysis finished with errors!')