[Haskell-cafe] Haskell Quiz Solution - Haskell Newbie Requesting Review

Brandon Moore brandonm at yahoo-inc.com
Thu Nov 9 14:22:30 EST 2006

Justin Bailey wrote:
> As part of the Ruby Quiz in Haskell solutions appearing on the wiki
> recently, I just a solution to Ruby Quiz #100 - create a bytecode
> interpreter for a simple expression language.
> Like I said, the code below parses simple integer arithmetic
> expressions and generates byte codes for a hypothetical stack-based
> intepreter that would evaluate the expressions. To run it, save it as
> a literate haskell file and run "interpret_tests". That just shows
> correctness, though. Other output can be obtained by running
> "compile_tests" (shows bytes for all tests), "generate_tests"
> (symbolic bytecodes for all tests), and "eval_tests" (evaluate ASTs
> for all tests).
> To see the AST generated for a example expression, try something like
> 'parse "2-2-2"'.
> I'm just learning Haskell (about a month in) and if anyone has time
> and desire to critique the code below, I'd love to hear it. I come
> from an OOP (primarily C# & Ruby) background, so I'm really interested
> in getting a handle on the functional/Haskell "way" of coding. Thanks
> for any feedback!

I haven't had time to look over your code, but this reminds me of a fun 
"A type-correct, stack-safe, provably correct expression compiler in 
The code consists of an expression interpreter, a stack machine emulator,
a compiler, and a proof that forall expr, evaluate exper == execute 
(compile expr).
(proofs are functions - go Curry-Howard)
You can find the paper at http://www.cs.nott.ac.uk/~jjw/


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