68 lines
2.1 KiB
Plaintext
68 lines
2.1 KiB
Plaintext
module statics
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imports signatures/fostr-sig
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/** md
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Title: Adding Program Analysis with Statix
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## Development of fostr static analysis
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This section is more documentation of Spoofax in general and Statix
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in particular than of fostr itself, but is being maintained here in case
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it could be either helpful to someone getting started with Statix or
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helpful in understanding how the static characteristics of fostr were designed.
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As mentioned in the [Overview](../README.md), I don't like to program and a
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corollary of that is never to use a facility unless/until there's a need for
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it. So the first few rudimentary passes at fostr simply declared every program
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to be "OK" from the point of view of Statix:
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```statix
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{! "\git docs/statix_start:trans/statics.stx" extract:
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start: programOk
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stop: (.*TopLevel.*)
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!}
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```
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Then I reached the point at which the grammar was basically just
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```SDF3
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// Start.TopLevel = <Ex>
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// Ex.Sequence = sq:Ex+ {layout: align-list sq}
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// Ex.Terminated = <<Ex>;>
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{! "\git docs/statix_start:syntax/fostr.sdf3" extract:
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start: TermEx.Terminate
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stop: (.*bracket.*)
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!}
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```
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(The first three clauses are in comments because they approximate fostr's
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grammar; it actually uses a few more sorts for sequences of
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expressions, to acheive fostr's exact layout rules.)
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This was the first point at which there were two different types that might
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need to be written to standard output (Int and String), and although of course
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the dynamically-typed Python and Javascript code generated dealt with both fine,
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the Haskell code needed to differ depending on the
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type of the item written (and I hadn't even started OCaml code generation at
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that point since I knew it would be hopeless without statically typing fostr
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programs).
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So it was time to bite the bullet and add type checking via Statix to fostr.
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**/
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// see docs/implementation.md for detail on how to switch to multi-file analysis
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rules // single-file entry point
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programOk : Start
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programOk(TopLevel(_)).
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rules // multi-file entry point
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projectOk : scope
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projectOk(s).
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fileOk : scope * Start
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fileOk(s, TopLevel(_)).
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