class Interpreter(object):
def __init__(self, text):
self.parser = Parser(text)
def type_error(self, node):
raise Exception("No interpret_{} method".format(node.type))
def interpret_node(self, node):
""" interpret_node: interperts a given node. Note that this function
assumes that all the children of the node are present"""
method_name = "interpret_" + node.type
method_to_call = getattr(self, method_name, self.type_error)
return method_to_call(node)
def interpret_tree(self, tree):
"""interpret_tree: performs the calculations implied
by the given tree"""
def recurse(node):
for child in node.children:
recurse(child)
self.interpret_node(node)
recurse(tree.root)
def interpret_INTEGER(self, node):
pass
def interpret_PLUS(self, node):
node.type = INTEGER
left_child = node.children[0]
right_child = node.children[1]
node.value = left_child.value + right_child.value
def interpret_MINUS(self, node):
node.type = MINUS
left_child = node.children[0]
right_child = node.children[1]
node.value = left_child.value - right_child.value
def interpret_MUL(self, node):
node.type = MUL
left_child = node.children[0]
right_child = node.children[1]
node.value = left_child.value * right_child.value
def interpret_DIV(self, node):
node.type = INTEGER
left_child = node.children[0]
right_child = node.children[1]
node.value = left_child.value / right_child.value
def interpret(self):
self.parser.parse()
self.interpret_tree(self.parser.tree)
return self.parser.tree.root.value
class Interpreter(object):
def __init__(self, text):
self.parser = Parser(text)
def type_error(self, node):
raise Exception("No interpret_{} method".format(node.type))
def interpret_node(self, node):
""" interpret_node: interperts a given node. Note that this function
assumes that all the children of the node are present"""
method_name = "interpret_" + node.type
method_to_call = getattr(self, method_name, self.type_error)
return method_to_call(node)
def interpret_tree(self, tree):
"""interpret_tree: performs the calculations implied
by the given tree"""
def recurse(node):
for child in node.children:
recurse(child)
self.interpret_node(node)
recurse(tree.root)
def interpret_INTEGER(self, node):
pass
def interpret_PLUS(self, node):
node.type = INTEGER
left_child = node.children[0]
right_child = node.children[1]
node.value = left_child.value + right_child.value
def interpret_MINUS(self, node):
node.type = MINUS
left_child = node.children[0]
right_child = node.children[1]
node.value = left_child.value - right_child.value
def interpret_MUL(self, node):
node.type = MUL
left_child = node.children[0]
right_child = node.children[1]
node.value = left_child.value * right_child.value
def interpret_DIV(self, node):
node.type = INTEGER
left_child = node.children[0]
right_child = node.children[1]
node.value = left_child.value / right_child.value
def interpret(self):
self.parser.parse()
self.interpret_tree(self.parser.tree)
return self.parser.tree.root.value
def __init__(self, text):
self.parser = Parser(text)
def __init__(self, text):
self.parser = Parser(text)
