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SixtyPical/README.markdown
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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 released version of SixtyPical is 0.6. The current development
version of SixtyPical, unreleased as of this writing, is 0.7-PRE.
Documentation
-------------
* Design Goals — coming soon.
* [SixtyPical specification](doc/SixtyPical.md)
* [SixtyPical history](HISTORY.md)
* [Literate test suite for SixtyPical syntax](tests/SixtyPical Syntax.md)
* [Literate test suite for SixtyPical execution](tests/SixtyPical Execution.md)
* [Literate test suite for SixtyPical analysis](tests/SixtyPical Analysis.md)
* [Literate test suite for SixtyPical compilation](tests/SixtyPical Compilation.md)
* [6502 Opcodes used/not used in SixtyPical](doc/6502 Opcodes.md)
TODO
----
For 0.7:
* initialized `byte` memory locations
* initialized `byte table` memory locations
* `word` type.
* `word table` type.
For 0.8:
* zero-page memory locations.
* indirect addressing.
For 0.9
* save registers on stack or in memory (the preserves them = not trashed)
At some point...
* 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