# CS50 AI Problem 1A Invalid Syntax

For CS50AI Problem 1 (Knights), I am really confused as to what is producing this error.

Code:

``````from logic import *

AKnight = Symbol("A is a Knight")
AKnave = Symbol("A is a Knave")

BKnight = Symbol("B is a Knight")
BKnave = Symbol("B is a Knave")

CKnight = Symbol("C is a Knight")
CKnave = Symbol("C is a Knave")

# Puzzle 0
# A says "I am both a knight and a knave."
knowledge0 = And(
Or(AKnight, AKnave)
Biconditional(AKnight, Not(AKnave))
Biconditional(AKnave, Not(AKnight))

Implication(AKnight, And(AKinght, AKnave))
Implication(AKnave, Not(And(AKnight, AKnave)))
)

# Puzzle 1
# A says "We are both knaves."
# B says nothing.
knowledge1 = And(
Or(AKnight, AKnave)
Or(BKnight, BKnave)
Biconditional(AKnight, Not(AKnave))
Biconditional(BKnight, Not(BKnave))
Biconditional(AKnave, Not(AKnight))
Biconditional(BKnave, Not(BKnave))

Implication(AKnight, And(AKnave, BKnave))
Implication(AKnave, Not(And(AKnave, BKnave)))
)

# Puzzle 2
# A says "We are the same kind."
# B says "We are of different kinds."
knowledge2 = And(
Or(AKnight, AKnave)
Or(BKnight, BKnave)
Biconditional(AKnight, Not(AKnave))
Biconditional(BKnight, Not(BKnave))
Biconditional(AKnave, Not(AKnight))
Biconditional(BKnave, Not(BKnave))

Implication(AKnight, Or(And(AKnight, BKnight), And(AKnave, BKnave)))
Implication(AKnave, Not(Or(And(AKnight, BKnight), And(AKnave, BKnave))))
Implication(BKnight, Or(Not(And(AKnight, BKnight)), Not(And(AKnave, BKnave))))
Implication(BKnave, Not(Or(Not(And(AKnight, BKnight)), Not(And(AKnave, BKnave)))))
)

# Puzzle 3
# A says either "I am a knight." or "I am a knave.", but you don't know which.
# B says "A said 'I am a knave'."
# B says "C is a knave."
# C says "A is a knight."
knowledge3 = And(
Or(AKnight, AKnave)
Or(BKnight, BKnave)
Biconditional(AKnight, Not(AKnave))
Biconditional(BKnight, Not(BKnave))
Biconditional(CKnight, Not(CKnave))
Biconditional(AKnave, Not(AKnight))
Biconditional(BKnave, Not(BKnave))
Biconditional(CKnave, Not(CKnave))

Or(Implication(AKnight, AKnight), Implication(AKnight, AKnave))
Or(Implication(AKnave, Not(AKnight)), Implication(AKnave, Not(AKnave)))
Implication(BKnight, Or(Implication(AKnight, AKnave), Implication(AKnave, Not(AKnave)))
Implication(BKnave, Or(Not(Implication(AKnight, AKnave)), Not(Implication(AKnave, Not(AKnave))))
Implication(BKnight, CKnave)
Implication(BKnave, Not(CKnight))
Implication(CKnight, AKnight)
Implication(CKnave, Not(AKnave))
)

def main():
symbols = [AKnight, AKnave, BKnight, BKnave, CKnight, CKnave]
puzzles = [
("Puzzle 0", knowledge0),
("Puzzle 1", knowledge1),
("Puzzle 2", knowledge2),
("Puzzle 3", knowledge3)
]
for puzzle, knowledge in puzzles:
print(puzzle)
if len(knowledge.conjuncts) == 0:
print("    Not yet implemented.")
else:
for symbol in symbols:
if model_check(knowledge, symbol):
print(f"    {symbol}")

if __name__ == "__main__":
main()
``````

Error:

``````python puzzle.py
File "puzzle.py", line 16
Biconditional(AKnight, Not(AKnave))
^
SyntaxError: invalid syntax
``````

You have to provide commas to keep separate your logical expressions like

``` And(Or(AKnight, AKnave), Biconditional(AKnight, Not(AKnave)), Biconditional(AKnave, Not(AKnight)), Implication(AKnight, And(AKinght, AKnave)), Implication(AKnave, Not(And(AKnight, AKnave))) ) ``` This is the mistake in your logic.

The And() function takes multiple arguments. So when you do knowledge0 = And(x, y, z, etc) for example, you need to put commas in between x, y, and z, not just a new line.