alt Hacker NewsA genuine question: is the first point (flow typing / type narrowing) a subset of or intersection with or just an alias to SSA (static single assignment)? I'm playing with a small interpreted language implementation that is based on Lua, and have reached a point where I want to implement a single-pass SSA (there is a nice short CS paper on this), but cannot get my head around all the concepts, even if I need proper SSA for Typescript-like usability.
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prydt • yesterday at 7:16 PM
At least in my understanding of SSA, its a compiler implementation detail which makes writing optimizations simpler. I imagine you can implement flow typing without SSA.
Can you elaborate what you mean?
prydt • yesterday at 7:09 PM
What's the nice short paper? (I'd be interested in reading it!)
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No. Type systems are unrelated to abstract machines which are unrelated to usability.
Type inference/checking happens early in the pipeline.
SSA is a way of laying out assembly instructions for an abstract machine. I say abstract because real machines re-assign values to the same addresses over time (which is precisely what 'single' static assignment prescribes against). Once you know which registers your real machine has (and instructions), you could take your SSA and turn it into real assembly.
Also, "single-pass SSA"? Not to be too pedantic, but SSA is the destination, not the journey. You could take a single pass to transform from some expressions or statements into SSA, or perhaps from SSA into something else. What's the paper?