Casper: The Friendly Programming Language

Introduction

Welcome to Casper, a friendly scripting language designed to make high level programming a light and comfortable experience. This language incorporates a speech-like, easy-to-use syntax that eliminates unnecessary verboseness from the programming experience. Casper is reminiscent of Python with nuanced features and syntax designed to make its meaning as transparent as possible and make programming an entirely pleasant affair.

Casper is brought to you by Teddy Chu, Alexia Filler, Ian Lizarda, Donovan Moini, and Serena Zafiris.

If you like to see more about Casper, please check out Casper's official website at https://dmoini.github.io/casper/.

Check out our grammar: https://github.com/dmoini/casper/blob/master/syntax/casper.ohm

Features

• Scripting language
• Statically typed
• Partial type inference
• Parallel declaration and assignment
• Higher order functions
• Optional parameters

Types

Primitive types

• string
• boo (boolean)
• num
• list
• set
• dict (dictionary)

Variable Declaration and Assignment

Declaration

num x = 5

string y = "[email protected]"

boo z = true

list<string> teamMembers = ["Donovan", "Ian", "Teddy", "Serena", "Alexia", "Eddie from Playroll"]

set<string> awesomeLanguages = set("Casper", "Python", "JavaScript", "Nebula")

dict<string, string> professors = {"hustler": "Forney", "wizard": "Toal", "hates tests": "Dondi"}

num m, n = 1, 2

Assignment

x = 6

y = "[email protected]"

z = false

m, n = 3, 4

Function Declaration

void helloWorld():
    print("Hello world!")

void help(num x):
    for i from 0 to 10:
        print("help")

Operators

• add +
• subtract -
• multiply *
• divide /
• integer division //
• modulus %
• strict equality == or !=
• reference equality is
• less than <
• greater than >
• less than or equal <=
• greater than or equal >=
• logical AND and
• logical OR or
• logical NOT not or !

Ternary

a if b else c

print("isBig" if size > 9000 else "isSmall")

Conditional

if teamMembersAmount > 5:,
    print("Too many team members")
else if teamMembersAmount < 5:
    print("Not enough team members")
else:
    print("Just the right number of team members")

Loop

for x from 0 to 10:
    print(x)

for y from 0 to 10 by 2:
    print(y)

while true:
    print("I love casper")

Comments

~ this is a comment!

~*
this is a
multi-line comment
*~

Types of Static Semantic Errors

• Argument and parameter types do not match
• Break outside of loop
• Call is not a function
• Identifier already declared in this scope
• Incorrect function return type
• Incorrect number of arguments
• No return statement found
• Not a boolean
• Not a list or dictionary
• Not a number
• Number of ids does not equal number of exps
• Return statement not in function
• Set mixed types
• Types are not compatible
• Variable has not been declared
• Void functions cannot have return statements

Code Examples

Fibonacci Program

num fibonacci(num x):
    if (x <= 1):
        return x
    return fibonacci(x - 1) + fibonacci(x - 2)

function fibonacci(x) {
    if (x <= 1) {
        return x;
    }
    return fibonacci(x - 1) + fibonacci(x - 2);
}

Greatest Common Divisor

num gcd(num x, num y):
    num a = abs(x)
    num b = abs(y)
    while(b > 0):
        num t = b
        b = a % b
        a = t
    return a

function gcd(x, y) {
    let a = Math.abs(x);
    let b = Math.abs(y);
    while(b > 0) {
        let t = b;
        b = a % b;
        a = t;
    }
    return a;
}

First Factorial

num firstFactorial(num x):
    if (x == 0 or x == 1):
        return 1
    else:
        return x * firstFactorial(x - 1)

function firstFactorial(x) {
    if (x === 0 || x === 1) {
        return x
    }
    else {
        return x * firstFactorial(x - 1)
    }
}

Even or Odd

boo evenOrOdd(num x):
    return x % 2 == 0

function evenOrOdd(x) {
    return x % 2 == 0;
}

Area of a Circle

num areaOfCircle(num r):
   return pi() * r * r

function areaOfCircle(r) {
    return Math.PI * r * r;
}

Largest Number of Three

num largestNum(num x, num y, num z):
    if (x >= y and x >= z):
        return x
    else if (y >= x and y >= z):
        return y
    else:
        return z

function largestNum(x, y, z) {
    if (x >= y && x >= z) {
        return x;
    } else if (y >= x && y >= z) {
        return y;
    } else {
        return z;
    }
}

Two Sum

list<num> twoSum(list<num> nums, num target):
    if len(nums) == 2:
        return [0, 1]
    list<num> ans = []
    dict<num, num> hashTable = {}
    for i from 0 to len(nums):
        num complement = target - nums[i]
        num find = hashTable[complement]
        if hashTable.getValue(complement) != none:
            ans = [find, i]
            break
        hashTable[nums[i]] = i
    return ans

function twoSum(nums, target) {
    if (nums.length === 2) {
        return [0, 1];
    }
    let ans = [];
    let hashTable = {};
    for (let i = 0; i < nums.length; i++) {
        let complement = target - nums[i];
        let find = hashTable[complement];
        if (find !== undefined) {
            ans = [find, i];
            break;
        }
        hashTable[nums[i]] = i;
    }
	return ans;
};