"""
Scientific Calculator
A simple command-line calculator supporting arithmetic, trigonometric, and logarithmic operations.
"""

import math

def add(x, y):
    """Return the sum of x and y."""
    return x + y

def subtract(x, y):
    """Return the difference of x and y."""
    return x - y

def multiply(x, y):
    """Return the product of x and y."""
    return x * y

def divide(x, y):
    """Return the quotient of x and y."""
    if y == 0:
        raise ValueError("Cannot divide by zero.")
    return x / y

def sine(x):
    """Return the sine of x (in radians)."""
    return math.sin(x)

def cosine(x):
    """Return the cosine of x (in radians)."""
    return math.cos(x)

def tangent(x):
    """Return the tangent of x (in radians)."""
    return math.tan(x)

def logarithm(x, base=math.e):
    """Return the logarithm of x to the given base."""
    if x <= 0:
        raise ValueError("Logarithm undefined for non-positive values.")
    return math.log(x, base)

def exponent(x, y):
    """Return x raised to the power y."""
    return math.pow(x, y)

def main():
    print("Scientific Calculator")
    print("Select operation:")
    print("1. Add\n2. Subtract\n3. Multiply\n4. Divide\n5. Sine\n6. Cosine\n7. Tangent\n8. Logarithm\n9. Exponent\n0. Exit")
    while True:
        choice = input("Enter choice: ")
        try:
            if choice == '1':
                x, y = float(input("x: ")), float(input("y: "))
                print("Result:", add(x, y))
            elif choice == '2':
                x, y = float(input("x: ")), float(input("y: "))
                print("Result:", subtract(x, y))
            elif choice == '3':
                x, y = float(input("x: ")), float(input("y: "))
                print("Result:", multiply(x, y))
            elif choice == '4':
                x, y = float(input("x: ")), float(input("y: "))
                print("Result:", divide(x, y))
            elif choice == '5':
                x = float(input("x (radians): "))
                print("Result:", sine(x))
            elif choice == '6':
                x = float(input("x (radians): "))
                print("Result:", cosine(x))
            elif choice == '7':
                x = float(input("x (radians): "))
                print("Result:", tangent(x))
            elif choice == '8':
                x = float(input("x: "))
                base = input("Base (default e): ")
                base = float(base) if base else math.e
                print("Result:", logarithm(x, base))
            elif choice == '9':
                x, y = float(input("x: ")), float(input("y: "))
                print("Result:", exponent(x, y))
            elif choice == '0':
                print("Goodbye!")
                break
            else:
                print("Invalid choice.")
        except Exception as e:
            print(f"Error: {e}")

if __name__ == "__main__":
    main()