djhenderson / python-simple-vm

A simple virtual machine w/constant folding implemented in Python

This is the code from the blog post "Making a simple VM interpreter in Python", which you can find at https://csl.name/post/vm/

Made by Christian Stigen Larsen, with some improvements from the people at r/Python. Put in the public domain.

To run:

Hit CTRL+D or type "exit" to quit.
> 2 3 + 5 * println
Constant-folded (2 + 3) to 5
Constant-folded (5 * 5) to 25
25
> ^D

To test:

$ python vm.py test
Code before optimization: [2, 3, '+', 5, '*', 'println']
Constant-folded (2 + 3) to 5
Constant-folded (5 * 5) to 25
Code after optimization: [25, 'println']
Stack after running original program:
25
Data stack (top first):
Stack after running optimized program:
25
Data stack (top first):
Result: OK
** Program 1: Runs the code for `print((2+3)*4)`
20

** Program 2: Ask for numbers, computes sum and product.
Enter a number: 12
Enter another number: 13
Their sum is: 25
Their product is: 156

** Program 3: Shows branching and looping (use CTRL+D to exit).
Enter a number: 1
The number 1 is odd.
Enter a number: 2
The number 2 is even.
Enter a number: 3
The number 3 is odd.
Enter a number: ^D