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"Limits to Formal Methods","What Formal Methods CAN do"
"Formal methods are not a magic powder that you can sprinkle over your code to make it correct.","Formal methods are a structural backbone around which you can develop more robust code."
"Formal methods are only methods. You still need to apply them correctly, to the right things to have useful results.","When applied correctly, formal methods can eliminate not only single bugs, but entire classes of bugs and attacks, that your model can express as absent."
"Formal methods won’t prevent bugs on aspects of your code that you haven’t formalized yet.","Formal methods can ensure the non regression of your code with respect to those classes of defects you formalized. Unlike other methods, they provide a ratchet that ensures progress even as the code evolves."
"Formal methods can’t eliminate bugs and prevent attacks that go below the model you use (e.g. SPECTRE attack).","Formal methods allow you to reason at one high level of abstraction and transport your re

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;; works with Gerbil v0.12-DEV-1315-g5902327 on Gambit v4.8.8-434-g490f0a7d on nixpkgs 867d3f9 (gcc 7.2.0)
;; fails with Gerbil v0.12-DEV-1404-g0a266db on Gambit v4.8.8-435-gd1991ba7 on nixpkgs dafdaa9 (gcc 7.3.0)

package: bug

(export #t)
(import :clan/utils/assert)

(def foo (case-lambda (() 0) ((x) 1) ((x y) 2) ((x y z . t) (+ 3 (length t)))))

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#lang racket
(define-syntax defsyntax (syntax-rules () ((_ x ...) (define-syntax x ...))))

;; These two work:
(defsyntax Rnest
  (syntax-rules ()
    ((_ (rev ...) (one more ...)) (Rnest (one rev ...) (more ...)))
    ((_ () ()) ())
    ((_ (x) ()) x)
    ((_ (x (y ...) z ...) ()) (Rnest ((y ... x) z ...) ()))))

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# pkgs/development/compilers/gerbil/default.nix
# Note: this supposes Gambit was compiled with
#    "--enable-single-host"
#    "--enable-shared"
#    "--enable-absolute-shared-libs"
#    "--enable-c-opt=-O6" "--enable-gcc-opts" "--enable-inline-jumps"
#    "--enable-thread-system=posix" "--enable-dynamic-tls"
#    "--enable-openssl"

{ stdenv, fetchurl, fetchgit, gambit, openssl, zlib, coreutils, rsync }:

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trait IsContext {
  def contextualContent: List[HasContext[this.type]] = List()
  contextualContent.map { item => item.setContext(this) }
}
trait HasContext[+Context] {
  private var ctx: Any = null
  def setContext(context: Any) {
    assert(ctx == null)
    ctx = context
  }