Компиляторы пример из лекций

  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
%option noyywrap bison-bridge bison-locations
%{
#include <stdio.h>
#include <stdlib.h>
#define TAG_IDENT 1
#define TAG_NUMBER 2
#define TAG_KEYWORD 3
char *tag_names[] =
{
"END_OF_PROGRAM" , "IDENT" , "NUMBER" ,
"KEYWORD"
};
struct Position
{
int line , pos , index ;
};
void print_pos ( struct Position *p )
{
printf("(%d,%d)" ,p->line, p->pos);
}
struct Fragment
{
struct Position starting , following;
};
typedef struct Fragment YYLTYPE ;
void print_frag ( struct Fragment *f )
{
print_pos (&(f->starting));
printf ("-");
print_pos(&(f->following));
}
union Token {
char *ident; /* Бандитизм: должно быть int code; */
long num;
char ch;
};
typedef union Token YYSTYPE;
int continued;
struct Position cur;
#define YY_USER_ACTION \
{ \
int i; \
if (! continued) \
yylloc->starting = cur; \
continued = 0; \
\
for (i = 0; i < yyleng; i++) \
{ \
if (yytext[i] == '\n') \
{ \
cur.line++; \
cur.pos = 1; \
} \
else \
cur.pos++; \
cur.index++; \
} \
\
yylloc->following = cur; \
}
void init_scanner(char *program)
{
continued =0;
cur.line = 1;
cur.pos =1;
cur.index = 0;
yy_scan_string(program);
}
void err(char *msg)
{
printf("Error ");
print_pos(&cur);
printf(": %s\n",msg);
}
%}
LETTER [a-zA-Z]
DIGIT [0-9]
IDENT {LETTER}({LETTER}|{DIGIT})*
NUMBER {DIGIT}+
%x COMMENTS CHAR_1 CHAR_2
%%
[\n\t ]+
\/\* BEGIN(COMMENTS); continued =1;
<COMMENTS>[~*]* continued =1;
<COMMENTS>\*\/ {
print_frag(yylloc);
printf(" comment\n");
BEGIN(0);
}
<COMMENTS>\* continued = 1;
<COMMENTS><<EOF>> {
err("end of program found, '*/' expected");
return 0;
}
{IDENT} {
/* Бандитизм: здесь нужно поместить
идентификатор в словарь имён. */
yylval->ident = yytext;
return TAG_IDENT;
}
{NUMBER} {
/* Бандитизм: нет проверки на переполнение. */
yylval->num = atoi(yytext);
return TAG_NUMBER;
}
\' BEGIN(CHAR_1); continued = 1;
. err("unexpected character");
%%
#define PROGRAM "/* Expression */ alpha + 66666 blah "
int main ()
{
int tag;
YYSTYPE value;
YYLTYPE coords;
init_scanner (PROGRAM);
do
{
tag = yylex (&value ,&coords);
if (tag != 0)
{ }
}
while ( tag != 0);
return 0;
}