def sequence(self) -> Expr.Expr:
result = self.expression()
while self.match(COMMA):
operator = self.previous() # save the COMMA token
rhs = self.sequence() # and around we go!
result = Expr.Binary(result, operator, rhs)
return result
def addition(self) -> Expr.Expr:
result = self.multiplication()
while self.match(MINUS, PLUS):
# capture the -/+ that a successful match stepped over
operator = self.previous()
rhs = self.multiplication()
result = Expr.Binary(result, operator, rhs)
return result
def comparison(self) -> Expr.Expr:
result = self.addition()
while self.match(GREATER, GREATER_EQUAL, LESS, LESS_EQUAL):
# capture the one of those, that match stepped over
operator = self.previous()
rhs = self.addition()
result = Expr.Binary(result, operator, rhs)
return result
def multiplication(self) -> Expr.Expr:
result = self.unary()
while self.match(SLASH, STAR):
# capture the / or * that a successful match stepped over
operator = self.previous()
rhs = self.unary()
result = Expr.Binary(result, operator, rhs)
return result
def multiplication(self) -> Expr.Expr:
""" Parses a binary expression of multiplication precedence or higher"""
expr = self.unary()
while self.match(TokenType.SLASH, TokenType.STAR):
operator = self.previous()
right = self.unary()
expr = Expr.Binary(expr, operator, right)
return expr
def equality(self) -> Expr.Expr:
result = self.comparison()
while self.match(BANG_EQUAL, EQUAL_EQUAL):
# capture the != or == that successful match stepped over
operator = self.previous()
rhs = self.comparison()
result = Expr.Binary(result, operator, rhs)
return result
def main():
astPrinter = AstPrinter()
expression = Expr.Binary(
Expr.Unary(Token(TokenType.MINUS, '-', None, 1), Expr.Literal(123)),
Token(TokenType.STAR, '*', None, 1),
Expr.Grouping(Expr.Literal(45.67)))
print(astPrinter.print(expression))
def bitor(self) -> Expr.Expr:
""" Parses a binary expression of bitor precedence or higher """
expr = self.bitxor()
while self.match(TokenType.BAR):
operator = self.previous()
right = self.bitxor()
expr = Expr.Binary(expr, operator, right)
return expr
def addition(self) -> Expr.Expr:
""" Parses a binary expression of additive precedence or higher"""
expr = self.multiplication()
while self.match(TokenType.MINUS, TokenType.PLUS):
operator = self.previous()
right = self.multiplication()
expr = Expr.Binary(expr, operator, right)
return expr
def equality(self) -> Expr.Expr:
""" Parses a binary expression of equality precedence or higher"""
expr = self.comparison()
while self.match(TokenType.BANG_EQUAL, TokenType.EQUAL_EQUAL):
operator = self.previous()
right = self.comparison()
expr = Expr.Binary(expr, operator, right)
return expr
def addition(self) -> Expr.Expr:
expression = self.multiplication()
while self.match(Token.TokenType.MINUS, Token.TokenType.PLUS):
operator = self.previous()
right = self.multiplication()
expression = Expr.Binary(expression, operator, right)
return expression
def multiplication(self) -> Expr.Expr:
expression = self.unary()
while self.match(Token.TokenType.SLASH, Token.TokenType.STAR):
operator = self.previous()
right = self.unary()
expression = Expr.Binary(expression, operator, right)
return expression
def exp(self) -> Expr.Expr:
""" Parses an exponent expression """
expr = self.call()
while self.match(TokenType.STAR_STAR):
operator = self.previous()
right = self.call()
expr = Expr.Binary(expr, operator, right)
return expr
def bitshift(self) -> Expr.Expr:
""" Parses a binary expression of bitshift precedence or higher """
expr = self.addition()
while self.match(TokenType.GREATER_GREATER, TokenType.LESS_LESS):
operator = self.previous()
right = self.addition()
expr = Expr.Binary(expr, operator, right)
return expr
def factor(self):
expr = self.unary()
while self.match(TokenType.SLASH, TokenType.STAR):
operator = self.previous()
right = self.unary()
expr = Expr.Binary(expr, operator, right)
return expr
def term(self):
expr = self.factor()
while self.match(TokenType.PLUS, TokenType.MINUS):
operator = self.previous()
right = self.factor()
expr = Expr.Binary(expr, operator, right)
return expr
def equality(self):
expr = self.comparison()
while self.match(TokenType.BANG_EQUAL, TokenType.EQUAL_EQUAL):
operator = self.previous()
right = self.comparison()
expr = Expr.Binary(expr, operator, right)
return expr
def comparison(self) -> Expr.Expr:
""" Parses a binary expression of comparitive precedence or higher"""
expr = self.bitor()
while self.match(TokenType.GREATER, TokenType.GREATER_EQUAL,
TokenType.LESS, TokenType.LESS_EQUAL):
operator = self.previous()
right = self.bitor()
expr = Expr.Binary(expr, operator, right)
return expr
def comparison(self) -> Expr.Expr:
expression = self.addition()
while self.match(Token.TokenType.GREATER,
Token.TokenType.GREATER_EQUAL, Token.TokenType.LESS,
Token.TokenType.LESS_EQUAL):
operator = self.previous()
right = self.addition()
expression = Expr.Binary(expression, operator, right)
return expression
def run_main():
exp = Expr.Binary(
Expr.Unary(
Token(TokenType.MINUS, "-", null, 1),
Expr.Litaral(123)),
Toke(TokenType.Star, "*", null, 1),
Expr.Grouping(
Expr.Literal(45.67)))
print(AstPrinter.print(exp))
def multiplication(self):
'''
Similar process to "equality" with the left and right operands recursively descending
from "unary".
We bundle again into an Expression syntax class and return
'''
expr = self.unary()
while self.match(TokenType.SLASH, TokenType.STAR):
operator = self.previous()
right = self.unary()
expr = Expr.Binary(expr, operator, right)
return expr
def comparison(self):
'''
Similar process to "equality" with the left and right operands recursively descending
from "addition".
We bundle again into an Expression syntax class and return
'''
expr = self.addition()
while self.match(TokenType.GREATER, TokenType.GREATER_EQUAL,
TokenType.LESS, TokenType.LESS_EQUAL):
operator = self.previous()
right = self.addition()
expr = Expr.Binary(expr, operator, right)
return expr
def comparison(self):
expr = self.term()
while self.match(
TokenType.GREATER,
TokenType.GREATER_EQUAL,
TokenType.LESS,
TokenType.LESS_EQUAL,
):
operator = self.previous()
right = self.term()
expr = Expr.Binary(expr, operator, right)
return expr
def equality(self):
'''
We call the comparison() rule first to define our left operand. After that's done,
which means it ended up in some type of "primitive" terminal, we can then check
if our tokens are "!=" or "==". We store that in our "operator" and, like the left
operand, do the same recursion for the right operand.
We bundle these operands and the operator into an Expression syntax class and return
'''
expr = self.comparison()
while self.match(TokenType.BANG_EQUAL, TokenType.EQUAL_EQUAL):
operator = self.previous()
right = self.comparison()
expr = Expr.Binary(expr, operator, right)
return expr
def comparison(self):
ast = self.addition()
while self.match(TokenType.GREATER, TokenType.GREATER_EQUAL,
TokenType.LESS, TokenType.LESS_EQUAL):
ast = Expr.Binary(ast, self.nextToken(), self.addition())
return ast
return self.parenthesize(expr.operator.lexeme, expr.left, expr.right)
def visit_Grouping(self, expr):
assert isinstance(expr, Expr.Grouping), "Must be Grouping Expression otherwise cannot print its AST"
return self.parenthesize("group", expr.expression)
def visit_Literal(self, expr):
assert isinstance(expr, Expr.Literal), "Must be Literal Expression otherwise cannot print its AST"
return str(expr.value)
def visit_Unary(self, expr):
assert isinstance(expr, Expr.Unary), "Must be Unary Expression otherwise cannot print its AST"
return self.parenthesize(expr.operator.lexeme, expr.right)
def parenthesize(self, name, *exprs):
builder = ["(", name]
for expr in exprs:
builder.append(expr.accept(self))
builder.append(")")
return " ".join(builder)
if __name__ == "__main__":
## Test Expression below
left_expression = Expr.Unary(Token(TokenType.MINUS, "-", 1, None), Expr.Literal(123))
operator = Token(TokenType.STAR, "*", 1, None)
right_expression = Expr.Grouping(Expr.Literal(45.67))
main_expression = Expr.Binary(left_expression, operator, right_expression)
print(ASTPrinter().print_ast(main_expression))
def multiplication(self):
ast = self.unary()
while self.match(TokenType.SLASH, TokenType.STAR):
ast = Expr.Binary(ast, self.nextToken(), self.unary())
return ast
def _test():
ast = Expr.Binary(
Expr.Unary(Token(TokenType.MINUS, "-", None, 1), Expr.Literal(123)),
Token(TokenType.STAR, "*", None, 1),
Expr.Grouping(Expr.Literal(45.67)))
print(LispPrinter().visit(ast))
def visit_binary_expr(self, expr: Expr.Binary):
return self.parenthesize(expr.operator.lexeme, expr.left, expr.right)
def visit_grouping_expr(self, expr: Expr.Grouping):
return self.parenthesize("group", expr.expression)
def visit_literal_expr(self, expr: Expr.Literal):
return str(expr.value) if expr.value != None else "nil"
def visit_unary_expr(self, expr: Expr.Unary):
return self.parenthesize(expr.operator.lexeme, expr.right)
def parenthesize(self, name: str, *expressions):
res = "(" + name
for expression in expressions:
res += " " + expression.accept(self)
res += ")"
return res
if __name__ == "__main__":
expression = Expr.Binary(
Expr.Unary(Token.Token(Token.TokenType.MINUS, "-", None, 1),
Expr.Literal(123)),
Token.Token(Token.TokenType.STAR, "*", None, 1),
Expr.Grouping(Expr.Literal(45.67)))
print(AstPrinter().print_ast(expression))
def addition(self):
ast = self.multiplication()
while self.match(TokenType.MINUS, TokenType.PLUS):
ast = Expr.Binary(ast, self.nextToken(), self.multiplication())
return ast