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SixtyPical

SixtyPical is a very low-level programming language, similar to 6502 assembly, with static analysis through abstract interpretation.

In practice, this means it catches things like

  • you forgot to clear carry before adding something to the accumulator
  • a subroutine that you call trashes a register you thought was preserved
  • you tried to write the address of something that was not a routine, to a jump vector

and suchlike. It also provides some convenient operations and abstractions based on common machine-language programming idioms, such as

  • copying values from one register to another (via a third register when there are no underlying instructions that directly support it)
  • explicit tail calls
  • indirect subroutine calls

The reference implementation can execute, analyze, and compile SixtyPical programs to 6502 machine code.

It is a work in progress, currently at the proof-of-concept stage.

The current development version of SixtyPical is 0.8-PRE.

Documentation

TODO

  • word table type.
  • vector table type.
  • zero-page memory locations.
  • indirect addressing.
  • low and high address operators (turn word type into byte.) Possibly.
  • save registers on stack or in memory (this preserves them = not trashed)

At some point...

  • initialized byte table memory locations
  • always analyze before executing or compiling, unless told not to
  • trash instruction.
  • interrupt routines.
  • 6502-mnemonic aliases (sec, clc)
  • other handy aliases (eq for z, etc.)
  • have copy instruction able to copy a constant to a user-def mem loc, etc.
  • add absolute addressing in shl/shr, absolute-indexed for add, sub, etc.
  • check and disallow recursion.
  • automatic tail-call optimization (could be tricky, w/constraints?)
  • re-order routines and optimize tail-calls to fallthroughs