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129 lines
5.1 KiB
Markdown
129 lines
5.1 KiB
Markdown
SixtyPical
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==========
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_Version 0.19. Work-in-progress, everything is subject to change._
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**SixtyPical** is a [low-level](#low-level) programming language
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supporting a [sophisticated static analysis](#sophisticated-static-analysis).
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Its reference compiler can generate [efficient code](#efficient-code) for
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several 6502-based [target platforms](#target-platforms) while catching many
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common mistakes at compile-time, reducing the time spent in debugging.
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Quick Start
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-----------
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Make sure you have Python (2.7 or 3.5+) installed. Then
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clone this repository and put its `bin` directory on your
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executable search path. Then you can run:
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sixtypical
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If you have the [VICE][] emulator installed, 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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Features
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--------
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SixtyPical 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.
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### Low level
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Many of SixtyPical's primitive instructions resemble those of the
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[MOS Technology 6502][] — it is in fact intended to be compiled to 6502
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machine code. However, it also does provide some "higher-level" operations
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based on common 8-bit machine-language programming idioms, including
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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)
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* copying, adding, and comparing 16-bit values (done in two steps)
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* explicit tail calls
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* indirect subroutine calls
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While a programmer will find these constructs convenient, their
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inclusion in the language is primarily to make programs easier to analyze.
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### Sophisticated static analysis
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The language defines an [effect system][], and the reference
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compiler [abstractly interprets][] the input program to check that
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it conforms to it. It can detect common mistakes 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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### Efficient code
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Unlike most languages, in SixtyPical the programmer must manage memory very
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explicitly, selecting the registers and memory locations to store all data in.
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So, unlike a C compiler such as [cc65][], a SixtyPical compiler doesn't need
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to generate code to handle [calling conventions][] or [register allocation][].
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This results in smaller (and thus faster) programs.
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The flagship demo, a minigame for the Commodore 64, compiles to
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a **930**-byte `.PRG` file.
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### Target platforms
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The reference implementation can analyze and compile SixtyPical programs to
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6502 machine code formats which can 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][]
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* [Apple II series][]
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For example programs for each of these, see [eg/README.md](eg/README.md).
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Documentation
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-------------
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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.
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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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[MOS Technology 6520]: https://en.wikipedia.org/wiki/MOS_Technology_6502
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[effect system]: https://en.wikipedia.org/wiki/Effect_system
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[abstractly interprets]: https://en.wikipedia.org/wiki/Abstract_interpretation
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[calling conventions]: https://en.wikipedia.org/wiki/Calling_convention
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[register allocation]: https://en.wikipedia.org/wiki/Register_allocation
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[VICE]: http://vice-emu.sourceforge.net/
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[cc65]: https://cc65.github.io/
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[Commodore 64]: https://en.wikipedia.org/wiki/Commodore_64
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[Commodore VIC-20]: https://en.wikipedia.org/wiki/Commodore_VIC-20
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[Atari 2600]: https://en.wikipedia.org/wiki/Atari_2600
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[Apple II series]: https://en.wikipedia.org/wiki/Apple_II_series
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