mirror of
https://github.com/servo/servo.git
synced 2025-08-05 21:50:18 +01:00
Update ply
This commit is contained in:
parent
4d393612b4
commit
2acdeabaf5
60 changed files with 9624 additions and 297 deletions
|
@ -0,0 +1,132 @@
|
|||
# -----------------------------------------------------------------------------
|
||||
# calc.py
|
||||
#
|
||||
# A calculator parser that makes use of closures. The function make_calculator()
|
||||
# returns a function that accepts an input string and returns a result. All
|
||||
# lexing rules, parsing rules, and internal state are held inside the function.
|
||||
# -----------------------------------------------------------------------------
|
||||
|
||||
import sys
|
||||
sys.path.insert(0, "../..")
|
||||
|
||||
if sys.version_info[0] >= 3:
|
||||
raw_input = input
|
||||
|
||||
# Make a calculator function
|
||||
|
||||
|
||||
def make_calculator():
|
||||
import ply.lex as lex
|
||||
import ply.yacc as yacc
|
||||
|
||||
# ------- Internal calculator state
|
||||
|
||||
variables = {} # Dictionary of stored variables
|
||||
|
||||
# ------- Calculator tokenizing rules
|
||||
|
||||
tokens = (
|
||||
'NAME', 'NUMBER',
|
||||
)
|
||||
|
||||
literals = ['=', '+', '-', '*', '/', '(', ')']
|
||||
|
||||
t_ignore = " \t"
|
||||
|
||||
t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
|
||||
|
||||
def t_NUMBER(t):
|
||||
r'\d+'
|
||||
t.value = int(t.value)
|
||||
return 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
|
||||
lexer = lex.lex()
|
||||
|
||||
# ------- Calculator parsing rules
|
||||
|
||||
precedence = (
|
||||
('left', '+', '-'),
|
||||
('left', '*', '/'),
|
||||
('right', 'UMINUS'),
|
||||
)
|
||||
|
||||
def p_statement_assign(p):
|
||||
'statement : NAME "=" expression'
|
||||
variables[p[1]] = p[3]
|
||||
p[0] = None
|
||||
|
||||
def p_statement_expr(p):
|
||||
'statement : expression'
|
||||
p[0] = 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] = variables[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")
|
||||
|
||||
# Build the parser
|
||||
parser = yacc.yacc()
|
||||
|
||||
# ------- Input function
|
||||
|
||||
def input(text):
|
||||
result = parser.parse(text, lexer=lexer)
|
||||
return result
|
||||
|
||||
return input
|
||||
|
||||
# Make a calculator object and use it
|
||||
calc = make_calculator()
|
||||
|
||||
while True:
|
||||
try:
|
||||
s = raw_input("calc > ")
|
||||
except EOFError:
|
||||
break
|
||||
r = calc(s)
|
||||
if r:
|
||||
print(r)
|
Loading…
Add table
Add a link
Reference in a new issue