CODE SHOULD BE IN PYTHON it should pass this test case: e = ('*', ('+', 'x', 2), ('/', 'x', 'yay')) assert variables(e) == {'x', 'yay'}
CODE SHOULD BE IN PYTHON it should pass this test case: e = ('*', ('+', 'x', 2), ('/', 'x', 'yay')) assert variables(e) == {'x', 'yay'}
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
Related questions
Question
write a function variables such that, if e is an expression, variables(e) is the set of variables that appear in it.
def variables():
CODE SHOULD BE IN PYTHON
it should pass this test case:
e = ('*', ('+', 'x', 2), ('/', 'x', 'yay'))
assert variables(e) == {'x', 'yay'}
![[8] def simplify(e):
if isinstance(e, tuple):
op, l, r = e
# We simplify the children expressions.
11 = simplify( Add text cell
simplify(r)
rr =
# We compute the expression if we can.
if isnumber(ll) and isnumber(rr) :
return calc(op, ll, rr)
else:
return (op, l1, rr)
else:
# Leaf. No simplification is possible.
return e](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fecf10a40-9173-4876-b1dc-0585f27b87b2%2Fea6bb02c-aaba-448c-903b-214e8d151439%2F7fim9fh_processed.png&w=3840&q=75)
Transcribed Image Text:[8] def simplify(e):
if isinstance(e, tuple):
op, l, r = e
# We simplify the children expressions.
11 = simplify( Add text cell
simplify(r)
rr =
# We compute the expression if we can.
if isnumber(ll) and isnumber(rr) :
return calc(op, ll, rr)
else:
return (op, l1, rr)
else:
# Leaf. No simplification is possible.
return e
![[2]
Os
class IllegalOperator(Exception):
pass
Let us define a helper function calc,which takes as argument an operator and two numbers, and computes the required operation. It will make
it easier to write the rest of the code.
def calc(op, left, right):
if op == "+":
return left + right
elif op ==
"_":
return left -
right
elif op ==
"*":
return left * right
elif op == "/":
return left / right
else:
raise IllegalOperator(op)
With this, we can write our compute method as follows.
[ 4] def compute(e):
if isinstance(e, tuple):
# We have an expression.
op, 1, r = e
# We compute the subexpressions.
11 = compute(1)
rr = compute(r)
# And on the basis of those, the whole expression.
return calc (op, 11, rr)
else:
# base expression; just return the number.
return e](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fecf10a40-9173-4876-b1dc-0585f27b87b2%2Fea6bb02c-aaba-448c-903b-214e8d151439%2F08hhh5_processed.png&w=3840&q=75)
Transcribed Image Text:[2]
Os
class IllegalOperator(Exception):
pass
Let us define a helper function calc,which takes as argument an operator and two numbers, and computes the required operation. It will make
it easier to write the rest of the code.
def calc(op, left, right):
if op == "+":
return left + right
elif op ==
"_":
return left -
right
elif op ==
"*":
return left * right
elif op == "/":
return left / right
else:
raise IllegalOperator(op)
With this, we can write our compute method as follows.
[ 4] def compute(e):
if isinstance(e, tuple):
# We have an expression.
op, 1, r = e
# We compute the subexpressions.
11 = compute(1)
rr = compute(r)
# And on the basis of those, the whole expression.
return calc (op, 11, rr)
else:
# base expression; just return the number.
return e
Expert Solution
Step 1
def variables(e):
e = ('*', ('+', 'x', 2), ('/', 'x', 'yay'));
assert variables(e) == {'x', 'yay'};
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