计算机代考程序代写 Haskell interpreter add more handouts and update index – cscodehelp代写

add more handouts and update index
mhe authored 1 month ago
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Runxy.md 2.18 KB
Runxy
This command line interface allows to run e.g.
$ runhaskell Runxy.hs factorial.xy 5
120
for the file factorial.xy. The usage is
runhaskell Runxy.hs
Alternatively, for faster execution time, you can compile
$ ghc –make Runxy.hs
and then run it with
$ ./Runxy
You can also use optimization options, such as
$ ghc –make -O2 Runxy.hs
Runxy.hs with
We name the module Main even though the file is called Runxy.hs , so that we can compile to produce an executable as explained above: module Main where
import System.Environment
We import the module System.Environment so that we can read the command line arguments with getArgs . We also need to import our own
modules:
import AbstractSyntax import Parser
import Interpreter
Because our little language doesn’t have IO facilities, we use the variable x to hold the input and the variable y to hold the output. So this function creates a storage with the value x for the variable “x” , and with all other variables uninitialized, giving an error if we try to use them:
initialStorage :: Integer -> Storage initialStorage x = update “x” x emptyStorage
Now, given a program in abstract syntax and a value for
runxy :: Program -> Integer -> Integer runxy p x = m’ “y”
where
m = initialStorage x m’ = run p m
x , we run it with the above interpreter, and extract the value of the variable
“y” .
Finally, the main function reads the command line arguments with getArgs , then uses the module Parser to parse the file, and the module Interpreter to run the syntax tree produced by the parser on the given integer:
main :: IO() main =

do
args <- getArgs if length args == 2 then do else putStrLn "Usage: runhaskell Runxy.hs ” Back to table of contents
concreteProgram <- readFile (args !! 0) let abstractProgram = parseProgram concreteProgram let x = read(args !! 1) let y = runxy abstractProgram x putStrLn (show y)