72 lines
2.0 KiB
Python
72 lines
2.0 KiB
Python
from .exceptions import JAPLError
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from .tokenobject import Token
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from .expression import Variable
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class Environment(object):
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"""
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A wrapper around a hashmap representing
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a scope
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"""
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def __init__(self, enclosing=None):
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"""Object constructor"""
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self.map = {}
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self.enclosing = enclosing
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def define(self, name: str, attr: object):
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"""Defines a new variable in the scope"""
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self.map[name] = attr
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def get(self, name: Token):
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"""Gets a variable"""
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if name.lexeme in self.map:
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return self.map[name.lexeme]
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elif self.enclosing:
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return self.enclosing.get(name)
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raise JAPLError(name, f"Undefined name '{name.lexeme}'")
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def get_at(self, distance, name):
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"""Gets a variable in a specific scope"""
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return self.ancestor(distance).map.get(name)
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def ancestor(self, distance):
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"""Finds the scope specified by distance"""
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env = self
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for _ in range(distance):
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env = env.enclosing
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return env
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def assign_at(self, distance, name, value):
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"""Same as get_at, but assigns instead of retrieving"""
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self.ancestor(distance).map[name.lexeme] = value
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def delete(self, var):
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"""Deletes a variable"""
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if var.name.lexeme in self.map:
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del self.map[var.name.lexeme]
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elif self.enclosing:
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self.enclosing.delete(var)
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else:
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raise JAPLError(var.name, f"Undefined name '{var.name.lexeme}'")
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def assign(self, name: Token, value: object):
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"""Assigns a variable"""
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if name.lexeme in self.map:
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if isinstance(value, Variable):
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self.map[name.lexeme] = self.get(value.name)
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else:
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self.map[name.lexeme] = value
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elif self.enclosing:
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self.enclosing.assign(name, value)
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else:
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raise JAPLError(name, f"Undefined name '{name.lexeme}'")
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