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from lexer import TokenType
class Expr:
def accept(self, visitor):
raise Exception("needs to be implemented")
class Literal:
def __init__(self, value):
self.value = value
def accept(self, visitor):
visitor.visitLiteral(self)
def __str__(self):
return f"{self.value}"
class Symbol:
def __init__(self, name):
self.name = name
def accept(self, visitor):
visitor.visitSymbol(self)
def __str__(self):
return f"'{self.name}"
class Nary:
def __init__(self, symbol, args):
self.symbol = symbol
self.args = args
def accept(self, visitor):
visitor.visitNary(self)
def __str__(self):
out = f"[{self.symbol} => ("
first = True
for arg in self.args:
if first:
out = f"{out} {arg}"
first = False
else:
out = f"{out}, {arg}"
return f"{out} )]"
class Binary:
def __init__(self, symbol, left, right):
self.symbol = symbol
self.left = left
self.right = right
def accept(self, visitor):
visitor.visitBinary(self)
class Visitor:
def visitLiteral(self, literal):
return literal.value
def visitBinary(self, binary):
sym = binary.symbol.text
left = binary.left.accept(self)
right = binary.right.accept(self)
return "({sym} {left} {right}"
def visitNary(self, nary):
sym = nary.symbol.text
args = []
for arg in nary.args:
args.append(arg.accept(self))
return "({sym} {' '.join(args)})"
def visitSymbol(self, symbol):
return symbol.name
def parseExpression(token, prev, tokens):
idx = 0
args = []
prev = token
while tokens[idx].type_ != TokenType.CLOSE_PAREN:
token = tokens[idx]
inc = 1
if token.type_ == TokenType.OPEN_PAREN:
expr, inc = parseExpression(token, prev, tokens[idx+1:])
args.append(expr)
elif token.type_ in (TokenType.STRING, TokenType.TRUE, TokenType.FALSE, TokenType.INT, TokenType.FLOAT):
expr, inc = parseLiteral(token, prev, tokens[idx+1:])
args.append(expr)
else:
expr, inc = parseSymbol(token, prev, tokens[idx+1:])
args.append(expr)
idx += inc
prev = token
return Expr.Nary(args[0], args[1:]), idx + 2 # parens
def parseSymbol(token, prev, tokens):
return Expr.Symbol(token.text), 1
def parseLiteral(token, prev, tokens):
return Expr.Literal(token.value), 1
def parse(tokens):
idx = 0
prev = None
exprs = []
while tokens[idx].type_ != TokenType.EOF:
token = tokens[idx]
counter = 1
if token.type_ == TokenType.OPEN_PAREN:
expr, counter = parseExpression(token, prev, tokens[idx+1:])
exprs.append(expr)
elif token.type_ in (TokenType.FALSE, TokenType.TRUE, TokenType.STRING, TokenType.INT, TokenType.FLOAT):
lit, counter = parseLiteral(token, prev, tokens[idx+1:])
exprs.append(lit)
else:
sym, counter = parseSymbol(token, prev, tokens[idx+1:])
exprs.append(sym)
idx += counter
prev = token
return exprs
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