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85 lines
3.5 KiB
Markdown
85 lines
3.5 KiB
Markdown
SixtyPical
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==========
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_Version 0.18. Work-in-progress, everything is subject to change._
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**SixtyPical** is a low-level programming language with advanced
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static analysis. Many of its primitive instructions resemble
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those of the 6502 CPU — in fact it is intended to be compiled to
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6502 machine code — but along with these instructions are
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constructs which ease structuring and analyzing the code. The
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language aims to fill this niche:
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* You'd use assembly, but you don't want to spend hours
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debugging (say) a memory overrun that happened because of a
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ridiculous silly error.
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* You'd use C or some other "high-level" language, but you don't
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want the extra overhead added by the compiler to manage the
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stack and registers.
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SixtyPical gives the programmer a coding regimen on par with assembly
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language in terms of size and hands-on-ness, but also able to catch
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many ridiculous silly errors at compile time, such as
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* you forgot to clear carry before adding something to the accumulator
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* a subroutine that you called trashes a register you thought it preserved
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* you tried to read or write a byte beyond the end of a byte array
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* you tried to write the address of something that was not a routine, to
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a jump vector
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Many of these checks are done with _abstract interpretation_, where we
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go through the program step by step, tracking not just the changes that
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happen during a _specific_ execution of the program, but _sets_ of changes
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that could _possibly_ happen in any run of the program.
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SixtyPical also provides some convenient operations based on
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machine-language programming idioms, such as
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* copying values from one register to another (via a third register when
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there are no underlying instructions that directly support it); this
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includes 16-bit values, which are copied in two steps
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* explicit tail calls
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* indirect subroutine calls
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SixtyPical is defined by a specification document, a set of test cases,
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and a reference implementation written in Python 2. The reference
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implementation can analyze and compile SixtyPical programs to 6502 machine
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code, which can be run on several 6502-based 8-bit architectures:
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* Commodore 64
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* Commodore VIC-20
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* Atari 2600 VCS
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* Apple II
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Quick Start
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-----------
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If you have the [VICE][] emulator installed, from this directory, you can run
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./loadngo.sh c64 eg/c64/hearts.60p
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and it will compile the [hearts.60p source code](eg/c64/hearts.60p) and
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automatically start it in the `x64` emulator, and you should see:
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You can try the `loadngo.sh` script on other sources in the `eg` directory
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tree, which contains more extensive examples, including an entire
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game(-like program); see [eg/README.md](eg/README.md) for a listing.
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[VICE]: http://vice-emu.sourceforge.net/
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Documentation
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-------------
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* [Design Goals](doc/Design%20Goals.md)
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* [SixtyPical specification](doc/SixtyPical.md)
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* [SixtyPical revision history](HISTORY.md)
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* [Literate test suite for SixtyPical syntax](tests/SixtyPical%20Syntax.md)
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* [Literate test suite for SixtyPical analysis](tests/SixtyPical%20Analysis.md)
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* [Literate test suite for SixtyPical compilation](tests/SixtyPical%20Compilation.md)
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* [Literate test suite for SixtyPical fallthru optimization](tests/SixtyPical%20Fallthru.md)
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* [6502 Opcodes used/not used in SixtyPical](doc/6502%20Opcodes.md)
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* [Output formats supported by `sixtypical`](doc/Output%20Formats.md)
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* [TODO](TODO.md)
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