<p>Python是一种非常容易调试的语言。你可以直接导入pdbpdb.settrace(). 在</p>
<p>然而,这些解析器生成器应该带有良好的调试工具。在</p>
<p><a href="http://www.antlr.org/" rel="nofollow noreferrer">http://www.antlr.org/</a></p>
<p><a href="http://www.dabeaz.com/ply/" rel="nofollow noreferrer">http://www.dabeaz.com/ply/</a></p>
<p><a href="http://pyparsing.wikispaces.com/" rel="nofollow noreferrer">http://pyparsing.wikispaces.com/</a></p>
<p><strong>回应悬赏</strong></p>
<p>下面是PLY调试的实际操作。在</p>
<p>源代码</p>
<pre><code>tokens = (
'NAME','NUMBER',
)
literals = ['=','+','-','*','/', '(',')']
# Tokens
t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
def t_NUMBER(t):
r'\d+'
t.value = int(t.value)
return t
t_ignore = " \t"
def t_newline(t):
r'\n+'
t.lexer.lineno += t.value.count("\n")
def t_error(t):
print("Illegal character '%s'" % t.value[0])
t.lexer.skip(1)
# Build the lexer
import ply.lex as lex
lex.lex(debug=1)
# Parsing rules
precedence = (
('left','+','-'),
('left','*','/'),
('right','UMINUS'),
)
# dictionary of names
names = { }
def p_statement_assign(p):
'statement : NAME "=" expression'
names[p[1]] = p[3]
def p_statement_expr(p):
'statement : expression'
print(p[1])
def p_expression_binop(p):
'''expression : expression '+' expression
| expression '-' expression
| expression '*' expression
| expression '/' expression'''
if p[2] == '+' : p[0] = p[1] + p[3]
elif p[2] == '-': p[0] = p[1] - p[3]
elif p[2] == '*': p[0] = p[1] * p[3]
elif p[2] == '/': p[0] = p[1] / p[3]
def p_expression_uminus(p):
"expression : '-' expression %prec UMINUS"
p[0] = -p[2]
def p_expression_group(p):
"expression : '(' expression ')'"
p[0] = p[2]
def p_expression_number(p):
"expression : NUMBER"
p[0] = p[1]
def p_expression_name(p):
"expression : NAME"
try:
p[0] = names[p[1]]
except LookupError:
print("Undefined name '%s'" % p[1])
p[0] = 0
def p_error(p):
if p:
print("Syntax error at '%s'" % p.value)
else:
print("Syntax error at EOF")
import ply.yacc as yacc
yacc.yacc()
import logging
logging.basicConfig(
level=logging.INFO,
filename="parselog.txt"
)
while 1:
try:
s = raw_input('calc > ')
except EOFError:
break
if not s: continue
yacc.parse(s, debug=1)
</code></pre>
<p>输出</p>
^{pr2}$
<p>分析表生成于解析器.out在</p>
<pre><code>Created by PLY version 3.2 (http://www.dabeaz.com/ply)
Grammar
Rule 0 S' -> statement
Rule 1 statement -> NAME = expression
Rule 2 statement -> expression
Rule 3 expression -> expression + expression
Rule 4 expression -> expression - expression
Rule 5 expression -> expression * expression
Rule 6 expression -> expression / expression
Rule 7 expression -> - expression
Rule 8 expression -> ( expression )
Rule 9 expression -> NUMBER
Rule 10 expression -> NAME
Terminals, with rules where they appear
( : 8
) : 8
* : 5
+ : 3
- : 4 7
/ : 6
= : 1
NAME : 1 10
NUMBER : 9
error :
Nonterminals, with rules where they appear
expression : 1 2 3 3 4 4 5 5 6 6 7 8
statement : 0
Parsing method: LALR
state 0
(0) S' -> . statement
(1) statement -> . NAME = expression
(2) statement -> . expression
(3) expression -> . expression + expression
(4) expression -> . expression - expression
(5) expression -> . expression * expression
(6) expression -> . expression / expression
(7) expression -> . - expression
(8) expression -> . ( expression )
(9) expression -> . NUMBER
(10) expression -> . NAME
NAME shift and go to state 1
- shift and go to state 2
( shift and go to state 5
NUMBER shift and go to state 3
expression shift and go to state 6
statement shift and go to state 4
state 1
(1) statement -> NAME . = expression
(10) expression -> NAME .
= shift and go to state 7
+ reduce using rule 10 (expression -> NAME .)
- reduce using rule 10 (expression -> NAME .)
* reduce using rule 10 (expression -> NAME .)
/ reduce using rule 10 (expression -> NAME .)
$end reduce using rule 10 (expression -> NAME .)
state 2
(7) expression -> - . expression
(3) expression -> . expression + expression
(4) expression -> . expression - expression
(5) expression -> . expression * expression
(6) expression -> . expression / expression
(7) expression -> . - expression
(8) expression -> . ( expression )
(9) expression -> . NUMBER
(10) expression -> . NAME
- shift and go to state 2
( shift and go to state 5
NUMBER shift and go to state 3
NAME shift and go to state 8
expression shift and go to state 9
state 3
(9) expression -> NUMBER .
+ reduce using rule 9 (expression -> NUMBER .)
- reduce using rule 9 (expression -> NUMBER .)
* reduce using rule 9 (expression -> NUMBER .)
/ reduce using rule 9 (expression -> NUMBER .)
$end reduce using rule 9 (expression -> NUMBER .)
) reduce using rule 9 (expression -> NUMBER .)
state 4
(0) S' -> statement .
state 5
(8) expression -> ( . expression )
(3) expression -> . expression + expression
(4) expression -> . expression - expression
(5) expression -> . expression * expression
(6) expression -> . expression / expression
(7) expression -> . - expression
(8) expression -> . ( expression )
(9) expression -> . NUMBER
(10) expression -> . NAME
- shift and go to state 2
( shift and go to state 5
NUMBER shift and go to state 3
NAME shift and go to state 8
expression shift and go to state 10
state 6
(2) statement -> expression .
(3) expression -> expression . + expression
(4) expression -> expression . - expression
(5) expression -> expression . * expression
(6) expression -> expression . / expression
$end reduce using rule 2 (statement -> expression .)
+ shift and go to state 12
- shift and go to state 11
* shift and go to state 13
/ shift and go to state 14
state 7
(1) statement -> NAME = . expression
(3) expression -> . expression + expression
(4) expression -> . expression - expression
(5) expression -> . expression * expression
(6) expression -> . expression / expression
(7) expression -> . - expression
(8) expression -> . ( expression )
(9) expression -> . NUMBER
(10) expression -> . NAME
- shift and go to state 2
( shift and go to state 5
NUMBER shift and go to state 3
NAME shift and go to state 8
expression shift and go to state 15
state 8
(10) expression -> NAME .
+ reduce using rule 10 (expression -> NAME .)
- reduce using rule 10 (expression -> NAME .)
* reduce using rule 10 (expression -> NAME .)
/ reduce using rule 10 (expression -> NAME .)
$end reduce using rule 10 (expression -> NAME .)
) reduce using rule 10 (expression -> NAME .)
state 9
(7) expression -> - expression .
(3) expression -> expression . + expression
(4) expression -> expression . - expression
(5) expression -> expression . * expression
(6) expression -> expression . / expression
+ reduce using rule 7 (expression -> - expression .)
- reduce using rule 7 (expression -> - expression .)
* reduce using rule 7 (expression -> - expression .)
/ reduce using rule 7 (expression -> - expression .)
$end reduce using rule 7 (expression -> - expression .)
) reduce using rule 7 (expression -> - expression .)
! + [ shift and go to state 12 ]
! - [ shift and go to state 11 ]
! * [ shift and go to state 13 ]
! / [ shift and go to state 14 ]
state 10
(8) expression -> ( expression . )
(3) expression -> expression . + expression
(4) expression -> expression . - expression
(5) expression -> expression . * expression
(6) expression -> expression . / expression
) shift and go to state 16
+ shift and go to state 12
- shift and go to state 11
* shift and go to state 13
/ shift and go to state 14
state 11
(4) expression -> expression - . expression
(3) expression -> . expression + expression
(4) expression -> . expression - expression
(5) expression -> . expression * expression
(6) expression -> . expression / expression
(7) expression -> . - expression
(8) expression -> . ( expression )
(9) expression -> . NUMBER
(10) expression -> . NAME
- shift and go to state 2
( shift and go to state 5
NUMBER shift and go to state 3
NAME shift and go to state 8
expression shift and go to state 17
state 12
(3) expression -> expression + . expression
(3) expression -> . expression + expression
(4) expression -> . expression - expression
(5) expression -> . expression * expression
(6) expression -> . expression / expression
(7) expression -> . - expression
(8) expression -> . ( expression )
(9) expression -> . NUMBER
(10) expression -> . NAME
- shift and go to state 2
( shift and go to state 5
NUMBER shift and go to state 3
NAME shift and go to state 8
expression shift and go to state 18
state 13
(5) expression -> expression * . expression
(3) expression -> . expression + expression
(4) expression -> . expression - expression
(5) expression -> . expression * expression
(6) expression -> . expression / expression
(7) expression -> . - expression
(8) expression -> . ( expression )
(9) expression -> . NUMBER
(10) expression -> . NAME
- shift and go to state 2
( shift and go to state 5
NUMBER shift and go to state 3
NAME shift and go to state 8
expression shift and go to state 19
state 14
(6) expression -> expression / . expression
(3) expression -> . expression + expression
(4) expression -> . expression - expression
(5) expression -> . expression * expression
(6) expression -> . expression / expression
(7) expression -> . - expression
(8) expression -> . ( expression )
(9) expression -> . NUMBER
(10) expression -> . NAME
- shift and go to state 2
( shift and go to state 5
NUMBER shift and go to state 3
NAME shift and go to state 8
expression shift and go to state 20
state 15
(1) statement -> NAME = expression .
(3) expression -> expression . + expression
(4) expression -> expression . - expression
(5) expression -> expression . * expression
(6) expression -> expression . / expression
$end reduce using rule 1 (statement -> NAME = expression .)
+ shift and go to state 12
- shift and go to state 11
* shift and go to state 13
/ shift and go to state 14
state 16
(8) expression -> ( expression ) .
+ reduce using rule 8 (expression -> ( expression ) .)
- reduce using rule 8 (expression -> ( expression ) .)
* reduce using rule 8 (expression -> ( expression ) .)
/ reduce using rule 8 (expression -> ( expression ) .)
$end reduce using rule 8 (expression -> ( expression ) .)
) reduce using rule 8 (expression -> ( expression ) .)
state 17
(4) expression -> expression - expression .
(3) expression -> expression . + expression
(4) expression -> expression . - expression
(5) expression -> expression . * expression
(6) expression -> expression . / expression
+ reduce using rule 4 (expression -> expression - expression .)
- reduce using rule 4 (expression -> expression - expression .)
$end reduce using rule 4 (expression -> expression - expression .)
) reduce using rule 4 (expression -> expression - expression .)
* shift and go to state 13
/ shift and go to state 14
! * [ reduce using rule 4 (expression -> expression - expression .) ]
! / [ reduce using rule 4 (expression -> expression - expression .) ]
! + [ shift and go to state 12 ]
! - [ shift and go to state 11 ]
state 18
(3) expression -> expression + expression .
(3) expression -> expression . + expression
(4) expression -> expression . - expression
(5) expression -> expression . * expression
(6) expression -> expression . / expression
+ reduce using rule 3 (expression -> expression + expression .)
- reduce using rule 3 (expression -> expression + expression .)
$end reduce using rule 3 (expression -> expression + expression .)
) reduce using rule 3 (expression -> expression + expression .)
* shift and go to state 13
/ shift and go to state 14
! * [ reduce using rule 3 (expression -> expression + expression .) ]
! / [ reduce using rule 3 (expression -> expression + expression .) ]
! + [ shift and go to state 12 ]
! - [ shift and go to state 11 ]
state 19
(5) expression -> expression * expression .
(3) expression -> expression . + expression
(4) expression -> expression . - expression
(5) expression -> expression . * expression
(6) expression -> expression . / expression
+ reduce using rule 5 (expression -> expression * expression .)
- reduce using rule 5 (expression -> expression * expression .)
* reduce using rule 5 (expression -> expression * expression .)
/ reduce using rule 5 (expression -> expression * expression .)
$end reduce using rule 5 (expression -> expression * expression .)
) reduce using rule 5 (expression -> expression * expression .)
! + [ shift and go to state 12 ]
! - [ shift and go to state 11 ]
! * [ shift and go to state 13 ]
! / [ shift and go to state 14 ]
state 20
(6) expression -> expression / expression .
(3) expression -> expression . + expression
(4) expression -> expression . - expression
(5) expression -> expression . * expression
(6) expression -> expression . / expression
+ reduce using rule 6 (expression -> expression / expression .)
- reduce using rule 6 (expression -> expression / expression .)
* reduce using rule 6 (expression -> expression / expression .)
/ reduce using rule 6 (expression -> expression / expression .)
$end reduce using rule 6 (expression -> expression / expression .)
) reduce using rule 6 (expression -> expression / expression .)
! + [ shift and go to state 12 ]
! - [ shift and go to state 11 ]
! * [ shift and go to state 13 ]
! / [ shift and go to state 14 ]
</code></pre>