# Boson

This my own programming language. Lexer, parser and interpreter were written using python.

Example factorial program using boson language is at examples folder.

To run Boson programs download this repo
-> Then run shell.py file in cmd i.e python shell.py
-> It will open the boson interpreter then pass the path of boson program to run function to execute boson programs.
   i.e run("examples\factorial.bs")

Boson has basic functionalities like,
  -> Arithmetic operations  (+, -, *, /, %, **(pow))
  -> Relational operations  (<, >, <=, >=, !=, ==)
  -> Logical operations  (and, or, not)
  -> Bitwise operations  (&, |, ^, ~)

Variables :

  -> The variables can be assigned using "assign" keyword.
     For example : assign a = 5

  -> The values of variables can be re-assigned using "$" symbol.
     For example : $a = 6

User input :

  -> The input from user can obtained by using input() function. For integer input we can use input_int() function.

Print :

  -> print function is used to print the output to the console screen.
  -> print function has 2 parameters which are output and separator.
     For example : print("Hello", " ")
                   print("world", "") # which prints "Hello world"
  -> "nl" used in separator for new line.
     For example : print("Hello", "nl")
                   print("world", "nl") # which prints "world" in next line followed by "Hello" in previous line. 

Lists :

  -> It supports basic functionalities like add an element, remove element, extend another list etc...
  -> Element of an list can be accessed using index value followed by "@" symbol.
     For example : assign l = [1, 2, 3, 4, 5]
	           print(l @ 0, "nl") # which returns the value of 0th index value i.e 1.
  -> Add an element to the list.
     1) Using append function.
        For example : append(l, 6) # which add 6 to the list l.
     2) Using "+" symbol.
        For example : l + 6 # same as append function.
  -> Remove an element from the list.
     1) Using pop function.
        For example : pop(l, 6) # which remove 6 from the list l.
     2) Using "-" symbol.
        For example : l - 6 # same as pop function.
  -> Extend an list to the another list.
     1) Using extend function.
        For example : extend(l1, l2) # which extend list l2 to the list l1.
     2) Using "*" symbol.
        For example : l1 * l2 # same as extend function.
  -> To find a length of the list use len function.
     For example : print(len(l), "nl") # which outputs the length of the list l.
  -> is_list() function returns true if the element passed to it is a list.

Strings :

  -> "+" is used to concat to strings.
     For example : print("Hello " + "world", "nl") # which outputs "Hello world".
  -> To embed the value of variable into the string use "{}"
     For example : assign num = 5
                   print("The number is : { num }", "nl") # which outputs "The number is : 5".
                   # if the variable is not declared then it prints the same i.e "The number is : { num }"
  -> is_str() function returns true if the element passed to it is a string.

For loop :

  -> for loop can be used to loop the block of statements for given number of times.
     For example : assign sum = 0
                   assign fact = 1
                   for i = 1 to 6 then
                    $fact = fact * i
                    $sum = sum + i
                   end
                   print(fact, ",")
                   print(sum, "nl") # loop runs from 1 to 5 and prints 15,120
  -> single statement can be used in for loop without new line.
     For example : for i = 1 to 6 then print(i, ",") # which prints 1,2,3,4,5
  -> step value can be used to jump values.
     For example : for i = 1 to 6 step 2 then print(i, ",") # which prints 1,3,5
  -> break and continue keywords also can be used.

While loop :

  -> while loop can be used to loop the block of statements for given number of times.
     For example : assign i = 0
                   while i < 6 then
                    $sum = sum + i
                    $i = i + 1
                   end
                   print(sum, "nl") # loop runs from 1 to 5 and prints 15
  -> break and continue keywords also can be used.

If statement :

  -> if used to run the block of statements if condition is true.
     For example : if 1 < 5 then
                    print("Hello", "nl") # which outputs Hello"
                   end
  -> elif can be used to check many conditions. Multiple elif can be used.
     For example : if 2 > 5 then
                    print("Hello", "nl")
                   elif 5 < 7 then
                    print("world", "nl") # which outputs "world"
  -> else can be used to run a block of code if the given conditions are false.
     For example : if 2 > 5 then
                    print("Hello", "nl")
                   else
                    print("world", "nl")
                   end # which outputs "world"

Functions :

  -> functions are be used to write a block of statements once and can be used it many number of times.
  -> func keyword is used to for function declaration. "->" is used for single line statement.
     For example : func sum(a, b) -> return a + b
                   sum(1,2) # which outputs 3
                   sum(3,4) # which outputs 7
  -> multi-line statements can be used in new line with end keyword.
     For example : func num(a, b)
                    print(a+b, ",")
                    print(a*b, "nl")
                   end
                   num(2,3) # which outputs 5,6
  -> anonymous also can be used and assign to a variable.
     For example : assign sum = func(a, b) -> return a + b
                   print(sum, "nl") # which outputs 
                   print(sum(1,2), "nl") # which outputs 3
  -> is_func() function returns true if the element passed to it is a function.

Example boson program for finding factorial of a number through iteration and recursion :

Output screenshot :