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from .expressions import Expression
class Statement:
def __init__(self):
pass
@classmethod
def from_tokens(cls, tokens: list) -> tuple:
for StatementClass in [LetStatement]:
stmt, dt = StatementClass.from_tokens(tokens)
if stmt is not None:
return (stmt, dt)
return (None, 0)
class LetStatement:
def __init__(self, name, expr):
self.name = name
self.expr = expr
@classmethod
def from_tokens(cls, tokens: list) -> tuple:
"""Construct let statement.
Format:
'let' <name> '=' <expression> ';'
"""
if len(tokens) < 5 or tokens[0] != "let":
return (None, 0)
name = tokens[1]
if name.type != "identifier":
raise JackSyntaxError(f"Expected variable name, got `{name}` instead", name)
if tokens[2] != "=":
raise JackSyntaxError(f"Expected `=`, got `{tokens[2]}` instead", tokens[2])
t = 3
expr, dt = Expression.from_tokens(tokens[t:])
if expr is None:
raise JackSyntaxError(f"Expected expression", tokens[3])
t += dt
if tokens[t] != ";":
raise JackSyntaxError(f"Expected `;`, got `{tokens[t]}` instead", tokens[t])
t += 1
return (LetStatement(name, expr), t)
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