Awesome

A simple compiler for Whitespace, for compiling from something that looks vaguely like assembly language into Whitespace.

Instructions are as follows, one per line:

• Stack manipulation:
  • PUSH <num>: Push <num> onto the stack.
  • DUPE: Duplicate the top item on the stack.
  • SWAP: Swap the top two items on the stack.
  • DROP: Discard the top item on the stack.
• Arithmetic: Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator.
  • ADD: Addition.
  • SUB: Subtraction.
  • MUL: Multiplication.
  • DIV: Integer division.
  • MOD: Modulo.
• Heap access: Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack.
  • STORE: Store.
  • RETRV: Retrieve.
• Flow control:
  • <label>: or LABEL <label>: Mark a location in the program.
  • GOSUB <label>: Call a subroutine.
  • JMP <label>: Jump unconditionally to a label.
  • JEZ <label>: Jump to a label if the top of the stack is zero.
  • JLZ <label>: Jump to a label if the top of the stack is negative.
  • RETURN: End a subroutine and transfer control back to the caller.
  • END: End the program.
• I/O:
  • PUTC: Output the character at the top of the stack.
  • PUTN: Output the number at the top of the stack.
  • GETC: Read a character and place it in the location given by the top of the stack.
  • GETN: Read a number and place it in the location given by the top of the stack.

Labels can be arbitrary strings of alphanumeric characters, plus - and _; the compiler will automatically convert them to Whitespace labels. Numbers should be decimal, optionally preceded by -.

Thus the annotated example given at the bottom of the Whitespace homepage is as follows:

PUSH 1      # Put a 1 on the stack
LABEL loop  # Set a Label at this point
DUPE        # Duplicate the top stack item
PUTN        # Output the current value
PUSH 10     # Put 10 (newline) on the stack...
PUTC        # ...and output the newline
PUSH 1      # Put a 1 on the stack
ADD         # Addition. This increments our current value.
DUPE        # Duplicate the value so we can test it
PUSH 11     # Push 11 onto the stack
SUB         # Subtraction. So if we've reached the end, we have a zero on the stack.
JEZ end     # If we have a zero, jump to the end
JMP loop    # Jump to the start
LABEL end   # Set the end label
DROP        # Discard our accumulator, to be tidy
END         # Finish