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
|
%token Tword Tif Telse Tbang
%token Targs
%token Tbasic Tparen Tblock
%define parse.error verbose
%{
#include "rc.h"
int yylex(void);
void yyerror(const char *);
%}
/* operator precendence: lowest first */
%right Telse
%left Twhile
%left '\n'
%left Tbang
%right '$'
/* semantic types */
%union{
struct Tree *tree;
}
%type<tree> line cmds cmdsln body paren block ifbody assign;
%type<tree> cmd basic executable nonkeyword keyword word atom arg args;
%type<tree> Tbang;
%type<tree> Tword Tif Telse;
/* grammar */
%start rc
%%
rc:
/*empty*/ { return 0; }
| line '\n' { return compile($1); }
line:
cmd
| cmds line { $$ = maketree2(';', $1, $2); }
body:
cmd
| cmdsln body { $$ = maketree2(';', $1, $2); }
paren:
'(' body ')' { $$ = maketree1(Tparen, $2); }
block:
'{' body '}' { $$ = maketree1(Tblock, $2); }
cmds:
cmd ';'
| cmd '&' { $$ = maketree1('&', $1); }
cmdsln:
cmds
| cmd '\n'
ifbody:
cmd %prec Telse { $$ = maketree2(Tif, nil, $1); }
| block Telse nl cmd { $$ = maketree3(Tif, nil, $1, $2); }
assign:
executable '=' word { $$ = maketree2('=', $1, $3); }
cmd:
/* empty */ %prec Twhile { $$ = nil; }
| basic { $$ = maketree1(Tbasic, $1); }
| block
| assign cmd %prec Tbang { $$ = hangchild1($1, $2, 2); }
| Tif paren nl ifbody { $$ = hangchild1($2, $1, 0); }
basic:
executable
| basic word { $$ = maketree2(Targs, $1, $2); }
arg: word
args:
arg
| args arg { $$ = maketree2(Targs, $1, $2); }
atom:
nonkeyword
| keyword { $$ = maketree1(Tword, $1); }
word:
atom
| word '^' atom { $$ = maketree2('^', $1, $3); }
executable:
nonkeyword
| executable '^' atom { $$ = maketree2('^', $1, $3); }
nonkeyword:
Tword
| '$' atom { $$ = maketree1('$', $2); }
keyword:
Tif|Telse
nl:
/*empty*/
| nl '\n'
%%
|
