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This commit is contained in:
David Beazley 2018-01-30 07:42:27 -06:00
parent 51b01d8335
commit d0e34417bc
2 changed files with 88 additions and 63 deletions
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45
README.txt
View File

@ -85,20 +85,27 @@ expressions and store variables:
from sly import Lexer, Parser
class CalcLexer(Lexer):
tokens = { NAME, NUMBER }
tokens = { NAME, NUMBER, PLUS, TIMES, MINUS, DIVIDE, ASSIGN, LPAREN, RPAREN }
ignore = ' \t'
literals = { '=', '+', '-', '*', '/', '(', ')' }
# Tokens
NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
NUMBER = r'\d+'
@_(r'\d+')
def NUMBER(self, t):
t.value = int(t.value)
return t
# Special symbols
PLUS = r'\+'
MINUS = r'-'
TIMES = r'\*'
DIVIDE = r'/'
ASSIGN = r'='
LPAREN = r'\('
RPAREN = r'\)'
@_(r'\n+')
def newline(self, t):
# Ignored pattern
ignore_newline = r'\n+'
# Extra action for newlines
def ignore_newline(self, t):
self.lineno += t.value.count('\n')
def error(self, t):
@ -109,15 +116,15 @@ expressions and store variables:
tokens = CalcLexer.tokens
precedence = (
('left', '+', '-'),
('left', '*', '/'),
('right', 'UMINUS'),
('left', PLUS, MINUS),
('left', TIMES, DIVIDE),
('right', UMINUS),
)
def __init__(self):
self.names = { }
@_('NAME "=" expr')
@_('NAME ASSIGN expr')
def statement(self, p):
self.names[p.NAME] = p.expr
@ -125,27 +132,27 @@ expressions and store variables:
def statement(self, p):
print(p.expr)
@_('expr "+" expr')
@_('expr PLUS expr')
def expr(self, p):
return p.expr0 + p.expr1
@_('expr "-" expr')
@_('expr MINUS expr')
def expr(self, p):
return p.expr0 - p.expr1
@_('expr "*" expr')
@_('expr TIMES expr')
def expr(self, p):
return p.expr0 * p.expr1
@_('expr "/" expr')
@_('expr DIVIDE expr')
def expr(self, p):
return p.expr0 / p.expr1
@_('"-" expr %prec UMINUS')
@_('MINUS expr %prec UMINUS')
def expr(self, p):
return -p.expr
@_('"(" expr ")"')
@_('LPAREN expr RPAREN')
def expr(self, p):
return p.expr
@ -158,7 +165,7 @@ expressions and store variables:
try:
return self.names[p.NAME]
except LookupError:
print("Undefined name '%s'" % p.NAME)
print(f'Undefined name {p.NAME!r}')
return 0
if __name__ == '__main__':

106
example/calc/calc.py
View File

@ -3,32 +3,32 @@
# -----------------------------------------------------------------------------
import sys
sys.path.insert(0, "../..")
sys.path.append('../..')
from sly import Lexer, Parser
class CalcLexer(Lexer):
# Set of token names. This is always required
tokens = { NUMBER, PLUS, MINUS, TIMES, DIVIDE, LPAREN, RPAREN }
# String containing ignored characters between tokens
tokens = { NAME, NUMBER, PLUS, TIMES, MINUS, DIVIDE, ASSIGN, LPAREN, RPAREN }
ignore = ' \t'
# Regular expression rules for tokens
PLUS = r'\+'
MINUS = r'-'
TIMES = r'\*'
DIVIDE = r'/'
LPAREN = r'\('
RPAREN = r'\)'
# Tokens
NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
NUMBER = r'\d+'
@_(r'\d+')
def NUMBER(self, t):
t.value = int(t.value)
return t
# Special symbols
PLUS = r'\+'
MINUS = r'-'
TIMES = r'\*'
DIVIDE = r'/'
ASSIGN = r'='
LPAREN = r'\('
RPAREN = r'\)'
@_(r'\n+')
def newline(self, t):
# Ignored pattern
ignore_newline = r'\n+'
# Extra action for newlines
def ignore_newline(self, t):
self.lineno += t.value.count('\n')
def error(self, t):
@ -36,50 +36,68 @@ class CalcLexer(Lexer):
self.index += 1
class CalcParser(Parser):
# Get the token list from the lexer (required)
tokens = CalcLexer.tokens
# Grammar rules and actions
@_('expr PLUS term')
precedence = (
('left', PLUS, MINUS),
('left', TIMES, DIVIDE),
('right', UMINUS)
)
def __init__(self):
self.names = { }
@_('NAME ASSIGN expr')
def statement(self, p):
self.names[p.NAME] = p.expr
@_('expr')
def statement(self, p):
print(p.expr)
@_('expr PLUS expr')
def expr(self, p):
return p.expr + p.term
return p.expr0 + p.expr1
@_('expr MINUS term')
@_('expr MINUS expr')
def expr(self, p):
return p.expr - p.term
return p.expr0 - p.expr1
@_('term')
@_('expr TIMES expr')
def expr(self, p):
return p.term
return p.expr0 * p.expr1
@_('term TIMES factor')
def term(self, p):
return p.term * p.factor
@_('expr DIVIDE expr')
def expr(self, p):
return p.expr0 / p.expr1
@_('term DIVIDE factor')
def term(self, p):
return p.term / p.factor
@_('factor')
def term(self, p):
return p.factor
@_('NUMBER')
def factor(self, p):
return p.NUMBER
@_('MINUS expr %prec UMINUS')
def expr(self, p):
return -p.expr
@_('LPAREN expr RPAREN')
def factor(self, p):
def expr(self, p):
return p.expr
@_('NUMBER')
def expr(self, p):
return int(p.NUMBER)
@_('NAME')
def expr(self, p):
try:
return self.names[p.NAME]
except LookupError:
print(f'Undefined name {p.NAME!r}')
return 0
if __name__ == '__main__':
lexer = CalcLexer()
parser = CalcParser()
while True:
try:
text = input('calc > ')
result = parser.parse(lexer.tokenize(text))
print(result)
except EOFError:
break
if text:
parser.parse(lexer.tokenize(text))