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interpreter.py
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interpreter.py
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import sys
from context import Context
from parser import Parser
import node_types as NodeType
from error import Error
from error_types import ErrorType
class Interpreter:
def __init__(self, ast, context):
self.ast = ast
self.context = context
def interpret(self, node, context):
for child in node:
if child == NodeType.PROGRAM:
return self.handle_program(node[child], context)
else:
return Error(ErrorType.INVALID_SYNTAX, "Expected program start token")
def handle_program(self, node, context):
"""
Execute first step of interpretation based on program keyword
:param node: the next level of the tree to visit
:param context: global context
:return: integer, float, string, or Error
"""
for child in node:
if child == NodeType.FUNCTION_DEFINITION:
pass
elif child == NodeType.RETURN:
return self.handle_return(node[child], context)
elif child == NodeType.IF:
return self.handle_expression(node[child], context)
else:
return Error(ErrorType.INVALID_SYNTAX, 'Program included invalid child nodes')
def handle_statement(self, node, context):
"""
Execute statement of function definition, if, or return and only return value if includes return statement
:param node: the next level of the tree to visit
:param context: global context
:return: integer, float, string, nothing, or Error
"""
for child in node:
if child == NodeType.FUNCTION_DEFINITION:
self.handle_statement(node[child], context)
if child == NodeType.IF:
self.handle_if(node[child], context)
if child == NodeType.RETURN:
return self.handle_expression(node[child], context)
else:
return Error(ErrorType.INVALID_SYNTAX, 'Statement included invalid child nodes')
def handle_function_definition(self, node, context):
"""
Identify function name, parameters, and statements and add to the function table in context of relevant scope
:param node: the next level of the tree to visit
:param context: global context
:return: integer, float, or string, or Error
"""
function_name = None
function_parameters = []
function_statements = []
function_variable_table = None
for child in node:
if child == NodeType.NAME:
function_name = node[child]
elif child == NodeType.PARAMETER:
function_parameters.append(node[child])
elif child == NodeType.STATEMENT:
function_statements.append(node[child])
elif child == NodeType.RETURN:
return self.handle_expression(node[child], context)
if function_name is None:
return Error(ErrorType.INVALID_SYNTAX, 'Defined function with no name for identifier')
if not function_statements:
return Error(ErrorType.INVALID_SYNTAX, 'Defined function with no statements')
context.function_table.add_function(function_name, function_parameters,
function_statements, function_variable_table)
def handle_if(self, node, context):
"""
Execute if statement evaluating the provided expression
If evaluation is true, execute all statements, if false, do nothing
:param node: the next level of the tree to visit
:param context: global context
:return: n/a
"""
expression = None
statements = []
for child in node:
if child == NodeType.EXPRESSION:
expression = self.handle_expression(node[child], context)
if child == NodeType.STATEMENT:
statements.append(self.handle_statement(node[child], context))
if expression is None:
return Error(ErrorType.INVALID_SYNTAX, "if statement has no expression to evaluate")
if not statements:
return Error(ErrorType.INVALID_SYNTAX, "if statement has no statements to execute")
if expression:
for statement in statements:
self.handle_statement(statement, context)
def handle_return(self, node, context):
"""
Execute return statement
:param node: the next level of the tree to visit
:param context: global context
:return: integer, float, or string
"""
return self.handle_expression(node[NodeType.EXPRESSION], context)
def handle_expression(self, node, context):
"""
Evaluate an expression composed of nested other types, but culminating in a number or string
:param node: the next level of the tree to visit
:param context: global context
:return: integer, float, or string
"""
for child in node:
if child == NodeType.NUMBER:
return node[NodeType.NUMBER]
elif child == NodeType.STRING:
return node[NodeType.STRING]
elif child == NodeType.FUNCTION_CALL:
return self.handle_function_call(node[child], context)
elif child == NodeType.BUILT_IN_FUNCTION:
return self.handle_built_in_function(node[child], context)
elif child == NodeType.PARAMETER:
return self.handle_parameter(node[child], context)
else:
return Error(ErrorType.INVALID_SYNTAX, "Expression contained invalid node type")
def handle_built_in_function(self, node, context):
"""
Identify which built_in_function to use (all are binary operators)
and call it on the two provided expressions, returning the result
:param node: the next level of the tree to visit
:param context: global context
:return: integer, float, or boolean
"""
function_name = None
expressions = []
for child in node:
if child == NodeType.EXPRESSION:
expressions.append(node[child])
if child == NodeType.EQUALITY:
if function_name is None:
function_name = NodeType.EQUALITY
else:
return Error(ErrorType.INVALID_SYNTAX, "More than one built in function name provided")
if child == NodeType.PLUS:
if function_name is None:
function_name = NodeType.PLUS
else:
return Error(ErrorType.INVALID_SYNTAX, "More than one built in function name provided")
if child == NodeType.MINUS:
if function_name is None:
function_name = NodeType.MINUS
else:
return Error(ErrorType.INVALID_SYNTAX, "More than one built in function name provided")
if function_name is None:
return Error(ErrorType.INVALID_SYNTAX, "No built in function name provided")
if len(expressions) != 2:
return Error(ErrorType.INVALID_SYNTAX, "Expected only two inputs for binary operation")
if function_name == NodeType.EQUALITY:
return self.handle_expression(expressions[0], context) == self.handle_expression(expressions[1], context)
elif function_name == NodeType.PLUS:
return self.handle_expression(expressions[0], context) + self.handle_expression(expressions[1], context)
elif function_name == NodeType.MINUS:
return self.handle_expression(expressions[0], context) - self.handle_expression(expressions[1], context)
return Error(ErrorType.INVALID_SYNTAX, "Unexpected built in function")
def handle_function_call(self, node, context):
"""
Identify function name, look up in function table in global context, and execute
:param node: the next level of the tree to visit
:param context: global context
:return: returns evaluation of function if there is a return statement, if not, returns nothing
"""
function_name = None
function_expressions = []
for child in node:
if child == NodeType.NAME:
function_name = node[child]
if child == NodeType.EXPRESSION:
function_expressions.append(node[child])
if function_name is None:
return Error(ErrorType.INVALID_SYNTAX, 'Called function without name as identifier')
if function_name not in context.function_table:
return Error(ErrorType.INVALID_SYNTAX, 'Called undefined function')
if len(function_expressions) != context.function_table.num_parameters:
return Error(ErrorType.INVALID_SYNTAX,
f"Function {function_name} expected {context.function_table.num_parameters} parameters " +
f"but received {len(function_expressions)} parameters")
function = context.function_table[function_name]
for statement in function.statements:
if NodeType.RETURN in statement:
return self.handle_statement(statement, context)
else:
self.handle_statement(statement, context)
def handle_parameter(self, node, context):
"""
Return string parameter
Not to useful right now, but potential for expansion and necessary if variables are added
:param node: the next level of the tree to visit
:param context: global context
:return: string
"""
return node
def main():
"""
Take in a file from user input, parse file and interpret parsed text, show output or error with details
:return: string, integer, float, or Error
"""
context = Context()
fn = None
if len(sys.argv) > 1:
index = 1
while index < len(sys.argv):
if sys.argv[index] == "-f" and len(sys.argv) >= index+1:
index += 1
fn = sys.argv[index]
index += 1
else:
print('Invalid or insufficient arguments')
parser = Parser(fn)
ast = parser.parse()
if type(ast) == Error:
print(ast)
return
interpreter = Interpreter(ast, context)
result = interpreter.interpret(ast, context)
print(result)
return result
main()