2017-11-21 11:13:21 +00:00
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Design Goals for SixtyPical
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===========================
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(draft)
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The intent of SixtyPical is to have a very low-level language that
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benefits from abstract interpretation.
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"Very low-level" means, on a comparable level of abstraction as
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assembly language.
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In the original vision for SixtyPical, SixtyPical instructions mapped
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nearly 1:1 to 6502 instructions. However, many times when programming
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in 6502 you're using idioms (e.g. adding a 16-bit constant to a 16-bit
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value stored in 2 bytes) and it's just massively easier to analyze such
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actions when they are represented by a single instruction.
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So SixtyPical instructions are similar to, inspired by, and have
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analogous restrictions as 6502 instructions, but in many ways, they
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are more abstract. For example, `copy`.
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The intent is that programming in SixtyPical is a lot like programming
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in 6052 assembler, but it's harder to make a stupid error that you have
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to spend a lot of time debugging.
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The intent is not to make it absolutely impossible to make such errors,
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just harder.
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2017-12-01 17:23:09 +00:00
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### Some Background ###
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The ideas in SixtyPical came from a couple of places.
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One major impetus was when I was working on [Shelta][], trying to cram
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all that code for that compiler into 512 bytes. This involved looking
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at the x86 registers and thinking hard about which ones were preserved
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when (and which ones weren't) and making the best use of that. And
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while doing that, one thing that came to mind was: I Bet The Assembler
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Could Track This.
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Another influence was around 2007 when "Typed Assembly Language" (and
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"Proof Carrying Code") were all the rage. I haven't heard about them
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in a while, so I guess they turned out to be research fads? But for a
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while there, it was all Necula, Necula, Necula. Anyway, I remember at
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the time looking into TAL and expecting to find something that matched
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the impression I had pre-formulated about what a "Typed Assembly"
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might be like. And finding that it didn't match my vision very well.
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I don't actually remember what TAL seemed like to me at the time, but
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what I had in mind was more like SixtyPical.
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(I'll also write something about abstract interpretation here at some
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point, hopefully.)
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