Your Own Language Challenge

When you type python my_program.py at the terminal, you're running a Python interpreter, that is, a program that understands Python and knows how to execute the code you wrote. Every programming language needs another program to translate it into something the computer's CPU can deal with.

For this challenge, you are going to write an interpreter for your own programming language, called "Pythonic" (from CSSI).

Read the Norvig article linked above. Read it again. This is the model we'll be following in this challenge. Read it a third time. We'll start Pythonic off with some simple math operations:

4 + 5
8 * 2 + 1
1 - 1 - 1 - 1 - 1
8 / 0

For now, executing a math expression like one of those above should print out the result to the user. Math in Pythonic should obey the standard order of operations. Once you get the basic ones, add more; Python's list is here. Add support for parenthesized math operations, so that 7 - 5 - 4 is different than 7 - (5 - 4). 3. Add logical operators like <, >, <=, >=, ==, and != to Cussy. These should yield values of True or False, like Python. 4. Add the ability to store the result of expressions to named variables and retrieve the value later. Code like this should now work:

a = 4 + 5
a * a * a - 7

However, this should be an error, since the frobnicate variable isn't defined yet:

4 + 8 * frobnicate

• Add support for calling functions in Cussy. Start off by defining a built-in print function (this will be your only function so far):

a = 4 + 5
print(a)

• Next up: if statements. These should look like this. Don't worry about else for now.

if (a < 5) {
    print(a)
}

Just like in Python, I should be able to do something like this:

b = a < 5 if (b) { print(a) }

7. Now add the ability to define your own functions to Pythonic. Start off easy and work your way up to more complex forms:

function my_function() {
    return 55
}

and then

function my_function(a) {
    return 55 + a
}

• Your major goal here is to be able to write and run this Pythonic code:

function factorial(val) {
    if (val <= 1) {
        return 1
    }
    return val * factorial(val - 1)
}
result = factorial(10)
print(result)