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
|
// Simple Example Scanner Class
package java_cup.simple_calc;
import java_cup.runtime.Symbol;
public class scanner implements java_cup.runtime.Scanner {
final java.io.InputStream instream;
public scanner(java.io.InputStream is) throws java.io.IOException {
instream = is;
}
public scanner() throws java.io.IOException { this(System.in); }
/* single lookahead character */
protected int next_char = -2;
/* advance input by one character */
protected void advance()
throws java.io.IOException
{ next_char = instream.read(); }
/* initialize the scanner */
private void init()
throws java.io.IOException
{ advance(); }
/* recognize and return the next complete token */
public Symbol next_token()
throws java.io.IOException
{
if (next_char==-2) init(); // set stuff up first time we are called.
for (;;)
switch (next_char)
{
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
/* parse a decimal integer */
int i_val = 0;
do {
i_val = i_val * 10 + (next_char - '0');
advance();
} while (next_char >= '0' && next_char <= '9');
return new Symbol(sym.NUMBER, new Integer(i_val));
case ';': advance(); return new Symbol(sym.SEMI);
case '+': advance(); return new Symbol(sym.PLUS);
case '-': advance(); return new Symbol(sym.MINUS);
case '*': advance(); return new Symbol(sym.TIMES);
case '/': advance(); return new Symbol(sym.DIVIDE);
case '%': advance(); return new Symbol(sym.MOD);
case '(': advance(); return new Symbol(sym.LPAREN);
case ')': advance(); return new Symbol(sym.RPAREN);
case -1: return new Symbol(sym.EOF);
default:
/* in this simple scanner we just ignore everything else */
advance();
break;
}
}
};
|
