"""Unary calculator REPL
MCS 260 Lecture 15 (2pm) - Emily Dumas
"""
# This was developed as a live coding example
# You can (and should) watch the video of it being 
# written at: 
# https://uic.zoom.us/rec/share/kPEoCrGkFWvAsYwVYU7d4fTzpAJUFmekVXyuGoXAXORCma-qI1LmTyAIr7sp3Ia5.8zOP7cXdPwdUJ5SM

def add(current, argument):
    """Add the argument to the current value"""
    return current+argument

def subtract(current, argument):
    """Subtract the argument from the current value"""
    return current-argument

def multiply(current, argument):
    """Multiply the argument and the current value"""
    return current*argument

def divide(current, argument):
    """Divide the current value by the argument"""
    return current/argument

def load(current, argument):
    """Return the argument"""
    return argument

# All known commands, mapping to the functions
# that handle them
commands = {
    "add": lambda c,a: c+a,
    "sub": subtract,
    "mul": multiply,
    "div": divide,
    "load": load,
    "power": lambda c,a: c**a,
}

# This variable stores the float on the calculator
# display, and we initialize it to 0.0
val = 0.0

while True:
    # print the current value
    print("{:12.3f}".format(val))
    # read a command
    s = input(">")

    if s == "exit":
        break

    if s == "help":
        print("I know about these commands:")
        for c in commands:
            print(c)
    else:
        # split the line into a command and argument    
        cmd,argstr = s.split()
        # convert the argument to a float
        arg = float(argstr)

        if cmd in commands:
            # Known command
            # If cmd is "add" and arg is 5
            # this will do  add(val,5)
            # If cmd is "mul" and arg is 5
            # this will do  multiply(val,5)
            val = commands[cmd](val,arg)
        else:
            print("ERROR: I don't know how to {}".format(cmd))