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Show HN: Computation at Compile-Time now free online

57 points by billsix 9y ago

billsix 9y ago
Author here. The book is about augmenting the Gambit Scheme compiler with the code which it is compiling, thus treating the compiler as an interpreter. Testing dominates the compile-time computation, as each procedure in the book is collocated with tests for that procedure. Should any test fail, the library fails to compile, like a type error in a statically-typed language.
- agumonkey 9y ago
  Thanks for this interesting topic. ps: is `[|y| (cons x y)]` standard notation in gambit ?
  - billsix 9y ago
    It is not. I made a preprocessor which expands "lambda literals" into lambdas. [|y| (cons x y)] turns into (lambda (y) (cons x y))
    - agumonkey 9y ago
      Thanks
- agumonkey 9y ago
  also one link causes https issues, but can be read through the WaybackMachine https://web.archive.org/web/20151012023906/http://mercure.iro.umontreal.ca/pipermail/gambit-list/2012-April/005917.html https://web.archive.org/web/20151012023906/http://mercure.ir...
  - billsix 9y ago
    Thanks! Will update
- dtornabene 9y ago
  this looks awesome, thanks for sharing it with the community for free. I've had it book marked from another site elsewhere for a couple weeks now, can't wait to get into it.
chriswarbo 9y ago
Looks very nice. I've recently written a bunch of Racket, which also encourages tests to be written alongside definitions, although they're not run as part of compilation. However, I've actually ended up with similar functionality, by packaging these scripts using Nix and having a dependency which runs the test suite and aborts on failure. It's nice to see more investigations going on into the nuances of programming "stages", rather than the usual compile vs interpret dogma. Another approach which seems similar in spirit is Zig's use of compile-time execution http://ziglang.org http://ziglang.org
k__ 9y ago
Coming from things like Babel I was really amazed what the OCaml compiler could do at compile time.
- billsix 9y ago
  With Gambit and libbug (my book), any computation can be done at compile time, including state and I/O :-)
  - k__ 9y ago
    Impossible O:
    - billsix 9y ago
      Not impossible, I do it in the book. I write both macro definitions and namespace declarations to file during compile time! :-)
kwhitefoot 9y ago
Sounds like an interesting idea. Reminds me a little of doctests in Python. This can also be applied to languages and compilers that do not allow the tests to run at compile time by wrapping the tests in #If DEBUG ... #End If or whatever the construct is in the language to compile the tests in debug mode only. Or define a special symbol WITHTESTS. Then at least your tests will be close by the code that they are testing and they won't affect the size of the delivered binary.
- billsix 9y ago
  Thanks for the reference on doctests. I encourage the collocation of tests with procedures in every language, but I personally doubt the efficacy of pound defines. Assert macros are great, but how can a programmer guarantee that they are ever even invoked? "mo' tests mo' problems" -Sean 'puff daddy" Combs.

57 points by billsix 9y ago

Author here. The book is about augmenting the Gambit Scheme compiler with the code which it is compiling, thus treating the compiler as an interpreter. Testing dominates the compile-time computation, as each procedure in the book is collocated with tests for that procedure. Should any test fail, the library fails to compile, like a type error in a statically-typed language.

agumonkey 9y ago
Thanks for this interesting topic. ps: is `[|y| (cons x y)]` standard notation in gambit ?
- billsix 9y ago
  It is not. I made a preprocessor which expands "lambda literals" into lambdas. [|y| (cons x y)] turns into (lambda (y) (cons x y))
  - agumonkey 9y ago
    Thanks
agumonkey 9y ago
also one link causes https issues, but can be read through the WaybackMachine https://web.archive.org/web/20151012023906/http://mercure.iro.umontreal.ca/pipermail/gambit-list/2012-April/005917.html https://web.archive.org/web/20151012023906/http://mercure.ir...
- billsix 9y ago
  Thanks! Will update
dtornabene 9y ago
this looks awesome, thanks for sharing it with the community for free. I've had it book marked from another site elsewhere for a couple weeks now, can't wait to get into it.

chriswarbo 9y ago

Looks very nice. I've recently written a bunch of Racket, which also encourages tests to be written alongside definitions, although they're not run as part of compilation. However, I've actually ended up with similar functionality, by packaging these scripts using Nix and having a dependency which runs the test suite and aborts on failure. It's nice to see more investigations going on into the nuances of programming "stages", rather than the usual compile vs interpret dogma. Another approach which seems similar in spirit is Zig's use of compile-time execution http://ziglang.org http://ziglang.org

k__ 9y ago

Coming from things like Babel I was really amazed what the OCaml compiler could do at compile time.

billsix 9y ago
With Gambit and libbug (my book), any computation can be done at compile time, including state and I/O :-)
- k__ 9y ago
  Impossible O:
  - billsix 9y ago
    Not impossible, I do it in the book. I write both macro definitions and namespace declarations to file during compile time! :-)

kwhitefoot 9y ago

Sounds like an interesting idea. Reminds me a little of doctests in Python. This can also be applied to languages and compilers that do not allow the tests to run at compile time by wrapping the tests in #If DEBUG ... #End If or whatever the construct is in the language to compile the tests in debug mode only. Or define a special symbol WITHTESTS. Then at least your tests will be close by the code that they are testing and they won't affect the size of the delivered binary.

billsix 9y ago
Thanks for the reference on doctests. I encourage the collocation of tests with procedures in every language, but I personally doubt the efficacy of pound defines. Assert macros are great, but how can a programmer guarantee that they are ever even invoked? "mo' tests mo' problems" -Sean 'puff daddy" Combs.