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
paper,
"A type-correct, stack-safe, provably correct expression compiler in
Epigram"
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/
Brandon
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