Lecture_2

# in this lecture we studied function 'definitions."

# ex 1:
def square(x):
    return mul(x,x)
    
def sum_squares(x,y):
    return add(square(x),square(y))

# // operator rounds the result down to integer

# A function definition can include some descriptions to help understanding.
def pressure(v,t,n):
    """Compute the pressure in pascals of an ideal gas.
    
    Applies the ideal gas law: http://en.wikipedia.org/wiki/Ideal_gas_law
    
    v -- volume of gas, in cubic meters
    t -- absolute temperature in degrees kelvin
    n -- particles of gas
    """
    k = 1.38e-23 # Boltzmann's constant
    return n * k * t / v
    
# we can call help(pressure) to retrieve all those descriptions. It's a good reference.

# note: we can set a value in arguments to some default values.

def pressure(v,t,n = 6)
    ~~~
    return n * k * t / v

pressure(2,3) # will take n = 6, v = 2, t = 3.
pressure(2,3,8) # will take n = 8, because a new value is given.

##############

# hw 1
# Q1 Goal:adding a to the absolute value of b, without calling abs:
from operator import add, sub
def a_plus_abs_b(a,b):
    """Return a+abs(b), but without calling abs.
    
    >>> a_plus_abs_b(2,3)
    5
    """
    if b < 0:
        op = sub
    else:
        op = add
    return op(a,b)

# Q2
def two_of_three(a,b,c):
    """Return x*x + y*y, where x and y are the two largest of a, b, c.
    
    >>> two_of_three(1,2,3)
    13
    """
    if a > b and b > c:
        twolarge = a**2 + b**2
    elif a > b and b < c:
        twolarge = a**2 + c**2
    else:
        twolarge = b**2 + c**2
    return twolarge
    
# Q3
def if_function(condition, true_result, false_result):
    """Return true_result if condition is a true value, and false_result otherwise."""
    if condition:
        return true_result
    else:
        return false_result

# Q4
def hailstone(n):
    """Print the hailstone sequence starting at n and return its length.

    >>> a = hailstone(10)  # Seven elements are 10, 5, 16, 8, 4, 2, 1
    10
    5
    16
    8
    4
    2
    1
    >>> a
    7
    """
	while n != 1:
		if n % 2 == 0:
			print(int(n))
			n = n / 2
		else:
			print(int(n))
			n = (n * 3) + 1
	else:
		return 1
		
#######

# Lecture 2 concluded.