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import sys
import calc
def eval_binary(frame, statement):
op = calc.condition_operator(statement)
left = eval_expression(frame, calc.condition_left(statement))
right = eval_expression(frame, calc.condition_right(statement))
if op == "+":
return left + right
elif op == "-":
return left - right
elif op == "*":
return left * right
elif op == "/":
return left / right
def eval_expression(frame, statement):
if calc.isconstant(statement):
if not (type(statement) is int or type(statement) is float):
print("{} is not a valid constant, need to be either int or float"
.format(statement))
sys.exit(-1)
return statement
elif calc.isvariable(statement):
if statement not in frame:
print("variable {} not declared".format(statement))
sys.exit(-1)
return frame[statement]
elif calc.isbinary(statement):
return eval_binary(frame, statement)
else:
print("{} is not valid syntax".format(statement))
sys.exit(-1)
def eval_assignment(frame, statement):
new_frame = frame.copy()
new_frame[calc.assignment_variable(statement)] = \
eval_expression(frame, calc.assignment_expression(statement))
return new_frame
def eval_condition(frame, statement):
op = calc.condition_operator(statement)
left = eval_expression(frame, calc.condition_left(statement))
right = eval_expression(frame, calc.condition_right(statement))
if op == ">":
return left > right
elif op == "<":
return left < right
elif op == "=":
return left == right
else:
print("{} is not valid syntax".format(statement))
sys.exit(-1)
def eval_repetition(frame, statement):
while eval_condition(frame, calc.repetition_condition(statement)):
frame = eval_statements(frame, calc.repetition_statements(statement))
return frame
def eval_selection(frame, statement):
if eval_condition(frame, calc.selection_condition):
frame = eval_statement(frame, calc.selection_true(statement))
elif calc.hasfalse(statement):
frame = eval_statement(frame, calc.selection_false(statement))
return frame
def eval_input(frame, statement):
new_frame = frame.copy()
var = calc.input_variable(statement)
val = input("Enter value for {}: ".format(var))
try:
new_frame[var] = int(val)
except ValueError:
try:
new_frame[var] = float(val)
except ValueError:
pass #TODO
return new_frame
def eval_output(frame, statement):
var = calc.output_variable(statement)
val = frame[var]
print("{} = {}".format(var, val))
def eval_statement(frame, statement):
if calc.isassignment(statement):
frame = eval_assignment(frame, statement)
elif calc.isrepetition(statement):
frame = eval_repetition(frame, statement)
elif calc.isselection(statement):
frame = eval_selection(frame, statement)
elif calc.isinput(statement):
frame = eval_input(frame, statement)
elif calc.isoutput(statement):
eval_output(frame, statement)
else:
print("{} is not valid syntax".format(statement))
sys.exit(-1)
return frame
def eval_statements(frame, statements):
frame = eval_statement(frame, calc.first_statement(statements))
if calc.empty_statements(calc.rest_statements(statements)):
return frame
else:
return eval_statements(frame, calc.rest_statements(statements))
def eval_program(program, frame={}):
if not calc.isprogram(program):
return
statements = calc.program_statements(program)
return eval_statements(frame, statements)
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