Own Programming Language

A simple compiler which compiles code written in my own programming language into MIPS-Assembler

This is a small project of mine without a real motivation except the learning experience during development itself. The project is currently in development and only partially functional. However, I will write a small tutorial on how to use my program.

How it works:

The compiler written in python reads from the file ´bsp.txt´, compiles the code and writes it in the file ´mips1.asm´. This file can then be opened with a MIPS-Simulator like Mars. You can try it out by following these steps:

• Open ´bsp.txt´ and write your code using the syntax explained in the next paragraph (then save the file).
• Run ´main.py´. An AST should get printed, which resembles your program.
• Now open ´mips1.asm´ using a MIPS-Simulator of your choice.

If there is no code in the .asm file, check if the function ´from_to_file()´ is called in ´main.py´ and correct if necessary.

Syntax

This is just some random syntax I like. It might not be the most logical or practical there is.

Basics

• No ; are needed
• C-style Braces {} for blocks
• # for comment and #[...]# for block comment

Arithmetic and Logic

The only type is int. Strings and floats are not yet implemented. Booleans are treated like ints, but you can use ´True´ or ´False´ as synonyms for 0 and 1.

• Binary operators: +, -, *, /, &&, ||, mod
• Unary operators: -, !
• Comparators: ==, !=, <, >, <=, >=

Variable Declaration, Initialisation and Assignment

Variables have a scope. However, every variable outside a function is global.

• Declaration: ´let x´
• Decl and Init: ´let x = 1´, ´const x = 1´
• Assignment: ´x = 1´

Control Flow

• if x < 10 {...}
• while x < 10 {...}
• do then while x < 10 {...}
• no break yet
• To create for-loops use ´for´ followed by your iteration counter identifier. Use an assignment expression or the ´from´ keyword to set a starting value (inclusive). Use ´to´ to mark an exclusive upper bound or ´while´ followed by an expression as a condition. The default step is 1, which can be modified by the ´then´ keyword followed by an assignment expression, which will be executed after each iteration. Examples:
  • for 10 {...} # executes 10 times
  • for i to 10 {...} # executes 10 times with i running from 0 to 9
  • for i from 5 to 10 # i runs from 5 to 9
  • for i = 5 while i <= 25 # i runs from 5 to 25
  • for i = 1 while i <= 64 then i=i*2 # i runs from 1 to 64 doubling in each iteration
• To iterate over a list use ´for each´ followed by your element identifier. Use ´in´ followed by a list to choose your list. You can also use ´index´ followed by an identifier. This index will count the iterations of the loop. Examples:
  • for each a in A {...}
  • for each a in [1, 3, 5] index i {...} # a will have the values 1, 3 and 5; i 0, 1, 2

Functions

Functions can take an infinite number of arguments and return one value. Functions can pass other functions as arguments and return values and can be declared locally in other functions.

• Declaration:
  • let a = func: () -> { ... return 1 }
  • let b = func: x -> {...}
  • let c = func: (x, y, z) -> {...}
• Call: ´aaa()´, ´ccc(x, y, z)´

Lists

• Decl and Init: ´let a = []´, ´let a = [1, 2, 3]´
• Getting an element: ´b = a[4]´
• Reassigning an element: ´a[4] = y´
• Binary operators:
  • Use ´push´ to append a list: ´a push 4´ (returns the appended list)
  • pop coming soon
  • Use ´add´ to append a list by a second list: ´a add b´ (returns the appended list)
• Unary operators:
  • ´len´ yields the length of the list: ´let lenOfA = len a´
  • ´copy´ returns a pointer to a copy of the list: ´let copyOfA = copy a´
  • ´pop´ returns the last element of the list and removes it from the list: ´let x = pop a´
• Comparators:
  • ´in´ checks if left argument is in right one: ´if x in [1, 2, 3] {...}´
  • ´equals´ checks if both lists have the same elements: ´if a equals b {...}´

If you find any bugs or want to share your opinion about this project, feel free to open a discussion or issue. And sorry if my code is full of mixed German and English.

Example Program --- Bubble Sort

´ func main: () -> { let A = [2, 4, 1, 6, 9, 5, 3] A = bubbleSort(A) print(A) }

func print: A -> { for each a in A { output a } }

func bubbleSort: A -> { let n = len A let swapped = True while ! swapped { swapped = False for i from 1 to n { if A[i-1] > A[i] { A = swap(A, i, i-1) swapped = True } } } return A }

func swap: (A, i, j) -> { let x = A[i] A[i] = A[j] A[j] = x return A }

main() ´