opvm

opvm is a simple stack based virtual machine written in rust.

Usage

Check main.rs to see how it's used.

Examples

Hello World:

push "Hello, World!"
print

Output: Hello, World!

Advanced Hello World:

push "Hello"
push ","
concat
push " "
concat
push "World!"
concat
print

Output: Hello, World!

Swap stack items

This will swap the top 2 stack items with each other.

push 0
push 1
print
print

Output:

1
0

Duplicate top of stack:

push 42
dup
print
print

Output:

42
42

Basic increment/decrement

push 5
inc
dup
print
dec
print

Output:

6
5

Loopy:

This program loops 5 times while counting the amount of loops it's done. It also has the ability to detect if the loop is > 1, and it will print a different string for how many loops were done.

#data
    .multi " loops!"            ; define our string for > 1 loops
    .single " loop!"            ; define our string for a single loop
    .looptimes 5                ; amount of times we are going to loop
#code
    .main
        push 0                  ; push 0 for start of loop counter
        jmp @loop               ; jump to start of the program
    .decideloopy
        dup                     ; duplicate counter
        push 1                  ; push 1 to compare counter
        jg @multi               ; compare counter, if 1, print single
        push @single            ; push our single string for printing
        ret
    .multi
        push @multi             ; push our multi string for printing
        ret
    .loop
        inc                     ; increment loop counter by 1
        dup                     ; duplicate loop counter for printing
        call @decideloopy       ; call into our .decideloopy function
        concat                  ; concat what text we decided on
        print                   ; X [loop|loops]!
        dup                     ; duplicate loop counter for comparing
        push @looptimes         ; push number of loops we expect
        jl @loop                ; less than expected, jump back to .loop to keep looping

Output:

1 loop!
2 loops!
3 loops!
4 loops!
5 loops!

Print stack size

push 0
dup
dup
dup
dup
load $__stack_size
push "stack size is: "
swap
concat
print

Output:

stack size is: 5

Heap allocation

push "My value I want on the heap"
alloc $my_heap_var
store $my_heap_var
load $__stack_size
print
load $my_heap_var
load $__stack_size
print
print

Output:

0
1
My value I want on the heap