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LIMPid.hs
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LIMPid.hs
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-- imports
import Prelude hiding ((+++))
import Data.Char
import System.IO
import Data.List (isPrefixOf)
getCh :: IO Char
getCh = do hSetEcho stdin False
c <- getChar
hSetEcho stdin True
return c
-- Definition of the environment: couple with name and value of the variables
type Env = [(String, String)]
-- Definition of the Parser: in input there are the Environment and the input string, and in output a triple
-- wich contains the Envoironment, the elaboration of the input and the rest of the input.
type Parser a = Env -> String -> [(Env, a, String)]
-- _____________________________________________________________________________________________________________________________________--
-- PARSER FUNCTIONS
-- _____________________________________________________________________________________________________________________________________--
-- "item" parses the first element of a list and return the rest of the list
item :: Parser Char
item = \env inp -> case inp of
[] -> []
(x:xs) -> [(env,x,xs)]
-- return a Parser after sostituting the elements of the expression a and Env of the triple with the input values
parserReturn :: Env -> a -> Parser a
parserReturn newenv v = \env inp -> [(newenv, v,inp)]
-- "failure" stops the parsing
failure :: Parser a
failure = \env inp -> []
-- CHOICE operator (+++). p +++ q execute p, otherwise if p fails executes q. Input and env are transferred from a parser to the other one
(+++) :: Parser a -> Parser a -> Parser a
p +++ q = \env inp -> case p env inp of
[] -> parse q env inp
[(env, v,out)] -> [(env, v,out)]
-- Executes the parsing
parse :: Parser a -> Env -> String -> [(Env, a,String)]
parse p env inp = p env inp
-- SEQUENCING operator (>>>=). parse p >>>= f fails if the application of the parser p to the input string fails, and otherwise applies the function f to the result value to give a
-- second parser, which is then applied to the output string to give the final result
(>>>=) :: Parser a -> (Env -> a -> Parser b ) -> Parser b --This is a MONAD (a box, a function applied to the element in the box, and a box as result in out)
p >>>= f = \env inp -> case parse p env inp of
[] -> [] -- If nothing (first parser) in input, parse nothing
[(env, v, out)] -> parse (f env v) env out -- If in input there is the triple, parse the application of the sec parser (function) to the unboxed element v
-- Parse a character if the predicate p is satisfied
sat :: (Char -> Bool) -> Parser Char
sat p = item >>>= \env x ->
if p x then
parserReturn env x
else
failure
-- Parse a specific character
char :: Char -> Parser Char
char x = sat (x ==)
-- _____________________________________________________________________________________________________________________________________--
-- ENVIRONMENT MANIPULATIONS
-- _____________________________________________________________________________________________________________________________________--
{- "setEnv" sets the environment adding or sobstituting a couple var-val
- v is the NAME of the variable
- a is the VALUE of the var (String type because it will be substituted in the string code)
- es is the environment -}
setEnv :: String -> String -> Env -> Env
setEnv v a [] = [(v,a)]
setEnv v a (e:es)
| (fst e)==v = [(v,a)] ++ es
| otherwise = e:(setEnv v a es)
{- "bind" is a function that interpeters all the variable in the env
-- es enviroment of variables
-- xs expression to evaluate -}
bind :: Env -> String -> String
bind [] xs = xs
bind es [] = []
bind (e:es) xs = bind es (replace e xs)
{- "replace" replaces a variable in the environment with its value
- v is the couple name,value of the variable
- xs is the expression to evaluate -}
replace :: (String,String) -> String -> String
replace v [] = []
replace v xs
| (fst v) `isPrefixOf` xs = (snd v) ++ replace v (drop (length (fst v)) xs)
| otherwise = (xs!!0) : replace v (drop 1 xs)
-- "getCode" extract the code (type of a) from the tuple --
getCode :: [(Env, a, String)] -> a
getCode [(_, x, _)] = x
-- extract the env state --
getMemory :: [(Env, a, String)] -> String
getMemory [] = []
getMemory [([], _, _)] = []
getMemory [(x:xs, c, s)] = fst x ++ "=>" ++ snd x ++ " " ++ (getMemory [(xs,c,s)])
-- extract the environment from the tuple --
getEnv :: [(Env, a, String)] -> Env
getEnv [] = []
getEnv [([], _, _)] = []
getEnv [(x, _, _)] = x
-- _____________________________________________________________________________________________________________________________________--
-- KEYWORDS AND SYMBOLS
-- _____________________________________________________________________________________________________________________________________--
-- Parse the "True" keyword
trueKeyword :: Parser String
trueKeyword = char 'T' >>>= \env _ -> char 'r' >>>= \_ _ -> char 'u' >>>= \_ _ -> char 'e' >>>= \_ _ -> parserReturn env ("True")
-- Parse the "False" keyword
falseKeyword :: Parser String
falseKeyword = char 'F' >>>= \env _ -> char 'a' >>>= \_ _ -> char 'l' >>>= \_ _ -> char 's' >>>= \_ _ -> char 'e' >>>= \_ _ -> parserReturn env ("False")
-- Parse the ""skip"" keyword
skipKeyword :: Parser String
skipKeyword = char 's' >>>= \env _ -> char 'k' >>>= \_ _ -> char 'i' >>>= \_ _ -> char 'p' >>>= \_ _ -> parserReturn env ("skip")
-- Parse the "if" keyword
ifKeyword :: Parser String
ifKeyword = char 'i' >>>= \env _ -> char 'f' >>>= \_ _ -> space >>>= \_ _ -> parserReturn env "if "
-- Parse the "else" keyword
elseKeyword :: Parser String
elseKeyword = char 'e' >>>= \env _ -> char 'l' >>>= \_ _ -> char 's' >>>= \_ _ -> char 'e' >>>= \_ _ -> space >>>= \_ _ -> parserReturn env "else "
-- Parse the "while" keyword
whileKeyword :: Parser String
whileKeyword = char 'w' >>>= \env _ -> char 'h' >>>= \_ _ -> char 'i' >>>= \_ _ -> char 'l' >>>= \_ _ -> char 'e' >>>= \_ _ -> space >>>= \_ s -> parserReturn env "while "
-- Parse the "do" keyword
doKeyword :: Parser String
doKeyword = char 'd' >>>= \env _ -> char 'o' >>>= \_ _ -> space >>>= \_ _ -> parserReturn env "do "
-- Parse the "for" keyword
forKeyword :: Parser String
forKeyword = char 'f' >>>= \env _ -> char 'o' >>>= \_ _ -> char 'r' >>>= \_ _ -> space >>>= \_ s -> parserReturn env "for "
-- Parse the "to" keyword
toKeyword :: Parser String
toKeyword = space >>>= \_ s -> char 't' >>>= \env _ -> char 'o' >>>= \_ _ -> space >>>= \_ s -> parserReturn env " to "
-- Parse the "times" keyword
timesKeyword :: Parser String
timesKeyword = space >>>= \_ s -> char 't' >>>= \env _ -> char 'i' >>>= \_ _ -> char 'm' >>>= \_ _ -> char 'e' >>>= \_ _ -> char 's' >>>= \_ _ -> space >>>= \_ s -> parserReturn env " times "
-- chars parsers
-- Parse the opened graf parentheses
openPargraf :: Parser String
openPargraf = char '{' >>>= \env _ -> space >>>= \_ _ -> parserReturn env ("{ ")
-- Parse the closed graf parentheses
closePargraf :: Parser String
closePargraf = char '}' >>>= \env _ -> parserReturn env ("}")
-- Parse open parentheses (with a possible space prefix)
openPar :: Parser String
openPar = char '(' >>>= \env _ -> parserReturn env "("
-- Parse closed parentheses (with a possible space prefix)
closePar :: Parser String
closePar = char ')' >>>= \env _ -> space >>>= \_ _ -> parserReturn env ") "
-- Parse colon
colon :: Parser String
colon = char ',' >>>= \env _ ->
(
space >>>= \_ _ ->
parserReturn env ", "
) +++
parserReturn env ","
-- Parse semicolon
semicolon :: Parser String
semicolon = char ';' >>>= \env _ ->
(
space >>>= \_ _ ->
parserReturn env "; "
) +++
parserReturn env ";"
-- Parse a space character
space :: Parser Char
space = char ' '
-- Parse a string of more spaces
spaces :: Parser String
spaces = char ' ' >>>= \env _ ->
parserReturn env " "
-- _____________________________________________________________________________________________________________________________________--
-- SYNTAX PARSING
-- _____________________________________________________________________________________________________________________________________--
-- ARITHMETIC EXPRESSIONS
-- Digit 0 - 9
digit :: Parser Char
digit = sat isDigit
-- Variable
-- variable ::= <letter> | <letter> <variabile>
variable :: Parser String
variable = sat isLetter >>>= \env c ->
(
char '[' >>>= \env op ->
variable >>>= \env v ->
char ']' >>>= \env cl ->
parserReturn env ([c] ++ "[" ++ bind env v ++ "]") -- in case array[var] we have to sobstitute the value var (dimension of array) in the env by using bind funct.
)
+++
(
char '[' >>>= \env op ->
parsenumber >>>= \env num ->
char ']' >>>= \env cl ->
parserReturn env ([c] ++ "[" ++ num ++ "]") -- in case array[n] we just have to parse the array with the dimension (parsenumber)
)
+++
(
variable >>>= \env f ->
parserReturn env ([c] ++ f)
)
+++
parserReturn env [c]
-- positive number made of one or more digits
-- positivenumber ::= <digit> | <digit> <positivenumber>
parsepositivenumber :: Parser String
parsepositivenumber = digit >>>= \env d -> (
parsepositivenumber >>>= \env n ->
parserReturn env ([d]++n)
)
+++ parserReturn env [d]
-- Integer number or variable
-- number ::= <positivenumber> | <variable>
parsenumber :: Parser String
parsenumber = parsepositivenumber +++ (variable >>>= \env v -> parserReturn env v) -- substitutes the variables with their values
-- Arithmetic positive factor made of integer numbers or arithmetic expression inside parentheses
-- apositivefactor ::= <number> | ( <aexp> )
parseapositivefactor :: Parser String
parseapositivefactor = (parsenumber >>>= \env n ->
parserReturn env n)
+++
(char '(' >>>= \env _ ->
parseaexpr >>>= \env e ->
char ')' >>>= \env _ ->
parserReturn env ("(" ++ e ++ ")")
)
-- Arithmetic negative factor made by negating positivefactor
-- anegativefactor ::= - | <apositivefactor>
parseanegativefactor :: Parser String
parseanegativefactor = char '-' >>>= \env _ ->
parseapositivefactor >>>= \env f ->
parserReturn env ("-" ++ f)
-- Arithmetic negative or positive factor
-- afactor ::= <apositivefactor> | <anegativefactor>
parseafactor :: Parser String
parseafactor = parseanegativefactor +++ parseapositivefactor
-- Arithmetic term made of arithmetic factors with moltiplication or division operator
-- aterm ::= <afactor> | <afactor> <aexpOp2> <aterm>
parseaterm :: Parser String
parseaterm = parseafactor >>>= \env f ->
(
char '*' >>>= \env _ ->
parseaterm >>>= \env t ->
parserReturn env (f ++ "*" ++ t)
)
+++
(
char '/' >>>= \env _ ->
parseaterm >>>= \env t ->
parserReturn env (f ++ "/" ++ t)
)
+++ parserReturn env f
-- Arithmetic expression made of arithmetic term with sum or substitution operator
-- aexpr ::= <aterm> | <aterm> <aexpOp1> <aexp>
parseaexpr :: Parser String
parseaexpr = parseaterm >>>= \env t ->
(
char '+' >>>= \env _ ->
parseaexpr >>>= \env e ->
parserReturn env (t ++ "+" ++ e)
)
+++
(
char '-' >>>= \env _ ->
parseaexpr >>>= \env e ->
parserReturn env (t ++ "-" ++ e)
)
+++ parserReturn env t
-- BOOLEAN EXPRESSIONS
-- Boolean factor made of Arithmetic expression combined by comparison operator
-- bfactor ::= <aexp> | <aexp> <comparisonOp> <aexp> | <variable>
parsebfactor :: Parser String
parsebfactor = (parseaexpr >>>= \env a1 ->
(
char '<' >>>= \env _ ->
parseaexpr >>>= \env a2 ->
parserReturn env ( a1 ++"<"++ a2)
)
+++
(
char '>' >>>= \env _ ->
parseaexpr >>>= \env a2 ->
parserReturn env (a1 ++">"++ a2)
)
+++
(
char '=' >>>= \env _ ->
parseaexpr >>>= \env a3 ->
parserReturn env (a1 ++"="++ a3)
) +++
(
char '<' >>>= \env _ ->
char '=' >>>= \env _ ->
parseaexpr >>>= \env a2 ->
parserReturn env ( a1 ++"<="++ a2)
)
+++
(
char '>' >>>= \env _ ->
char '=' >>>= \env _ ->
parseaexpr >>>= \env a2 ->
parserReturn env (a1 ++">="++ a2)
)
+++
(
char '!' >>>= \env _ ->
char '=' >>>= \env _ ->
parseaexpr >>>= \env a3 ->
parserReturn env (a1 ++"!="++ a3)
)
)
+++ (variable >>>= \env v ->
parserReturn env v)
-- Boolean term made of boolean factors, a boolean expression inside parentheses and negation operator
-- bterm ::= <bfactor> | ( <bexp> ) | ! <bexp>
parsebterm :: Parser String
parsebterm =
((trueKeyword +++ falseKeyword) >>>= \env b1 -> parserReturn env b1) +++
(parsebfactor >>>= \env b2 -> parserReturn env b2) +++
((trueKeyword +++ falseKeyword) >>>= \env b2 -> parserReturn env b2) +++
(char '(' >>>= \env _ -> parsebexpr >>>= \env b3 -> char ')' >>>= \env _ -> parserReturn env ( "(" ++ b3 ++ ")") ) +++
(char '!' >>>= \env _ -> parsebexpr >>>= \env b4 -> parserReturn env ("!"++ b4))
-- Boolean expression made of boolean terms with And and Or operator
-- bexp ::= <bterm> | <bterm> <bexpOp> <bexp>
parsebexpr :: Parser String
parsebexpr = parsebterm >>>= \env b1 ->
(
char '&' >>>= \env _ ->
parsebexpr >>>= \env b2 ->
parserReturn env ( b1 ++ "&" ++ b2)
)
+++
(
char '|' >>>= \env _ ->
parsebexpr >>>= \env b2 ->
parserReturn env (b1 ++ "|" ++ b2)
)
+++ parserReturn env b1
-- COMMAND EXPRESSIONS
-- assignment Command
-- assignmentcommand ::= <variable> := (<aexp> | <bexp>) <semicolon> | <letter> := { <array> } <semicolon>
parseassignmentCommand :: Parser String
parseassignmentCommand = variable >>>= \env v ->
char ':' >>>= \env _ ->
char '=' >>>= \env _ ->
(
parsebexpr >>>= \env b ->
semicolon >>>= \env s ->
parserReturn env (v ++ ":=" ++ b ++ s)
)
+++
(
parseaexpr >>>= \env a ->
semicolon >>>= \env s ->
parserReturn env (v ++ ":=" ++ a ++ s)
)
+++
( --parse the array explicit declaration
char '{' >>>= \env opg ->
parsearray >>>= \env arr -> --this function is defined after the parser of the assignment command
char '}' >>>= \env cpg ->
semicolon >>>= \env s ->
parserReturn env (v ++ ":=" ++ [opg] ++ arr ++ [cpg] ++ s)
)
-- Parses the array elements when an array is explicit declared as a sequence of factors
-- array ::= <afactor> | <afactor> <colon> <array>
parsearray :: Parser String
parsearray = parseafactor >>>= \env n ->
(
colon >>>= \env c ->
parsearray >>>= \env f ->
parserReturn env (n ++ c ++ f)
)
+++
parserReturn env (n)
-- if Command
-- ifcommand ::= if <space> ( <bexp> ) <space> then { <space> (<program> | <program> else { <space> <program>) } <semicolon>
parseifCommand :: Parser String
parseifCommand = ifKeyword >>>= \env i ->
openPar >>>= \env op ->
parsebexpr >>>= \env b ->
closePar >>>= \env cp ->
openPargraf >>>= \env t ->
parseprogram >>>= \env p1 ->
(
elseKeyword >>>= \env e ->
parseprogram >>>= \env p2 ->
closePargraf >>>= \env ei ->
semicolon >>>= \env se ->
parserReturn env (i ++ op ++ b ++ cp ++ t ++ p1 ++ e ++ p2 ++ ei ++ se)
) +++
(
closePargraf >>>= \env ei ->
semicolon >>>= \env se ->
parserReturn env (i ++ op ++ b ++ cp ++ t ++ p1 ++ ei ++ se)
)
-- While command
-- whilecommand ::= while <space> ( <bexp> ) <space> { <space> do <space> <program> <space> } <semicolon>
parsewhileCommand :: Parser String
parsewhileCommand = whileKeyword >>>= \env w ->
openPar >>>= \env op ->
parsebexpr >>>= \env b ->
closePar >>>= \env cp ->
openPargraf >>>= \env gr ->
doKeyword >>>= \env t1 ->
parseprogram >>>= \env p ->
closePargraf >>>= \env ew ->
semicolon >>>= \env s ->
parserReturn env (w ++ op ++ b ++ cp ++ gr ++ t1 ++ p ++ ew ++ s)
-- Do While command
-- dowhilecommand ::= do <space> { <space> do <space> <program> <space> } while <space> ( <bexp> ) <space> <semicolon>
parsedowhileCommand :: Parser String
parsedowhileCommand = doKeyword >>>= \env d ->
openPargraf >>>= \env opg ->
parseprogram >>>= \env p ->
closePargraf >>>= \env cpg ->
whileKeyword >>>= \env w ->
openPar >>>= \env op ->
parsebexpr >>>= \env b ->
closePar >>>= \env cp ->
semicolon >>>= \env s ->
parserReturn env (d ++ opg ++ p ++ cpg ++ w ++ op ++ b ++ cp ++ s)
-- For Times command
-- forcommand ::= for <space> <variable> <space> times <space> { <space> <program> <space> }
parseforCommand :: Parser String
parseforCommand = forKeyword >>>= \env f ->
variable >>>= \env v ->
timesKeyword >>>= \env t ->
openPargraf >>>= \env op ->
parseprogram >>>= \env p ->
closePargraf >>>= \env cp ->
semicolon >>>= \env s ->
parserReturn env (f ++ v ++ t ++ op ++ p ++ cp ++ s)
-- Command can be skip, assignment, if, while, do while or for times
-- command ::= <skipcommand> | <assignmentcommand> | <ifcommand> | <whilecommand> | <dowhilecommand> | <forcommand>
parsecommand :: Parser String
parsecommand = (skipCommand +++ parseassignmentCommand +++ parseifCommand +++ parsewhileCommand +++ parsedowhileCommand +++ parseforCommand) >>>= \env c ->
parserReturn env c
-- program ::= <command> | <command> <program>
parseprogram :: Parser String
parseprogram = parsecommand >>>= \env c -> ( parseprogram >>>= \env p -> parserReturn env (c ++ p)) +++ parserReturn env c
-- _____________________________________________________________________________________________________________________________________--
-- EXPRESSION'S EVALUATION
-- _____________________________________________________________________________________________________________________________________--
-- ARITHMETIC EXPRESSIONS
-- Positive number are made of one or more digits (SAME of the syntax parsing -> we have just to collect the string of the pos. number)
-- positivenumber ::= <digit> | <digit> <positivenumber>
positivenumber :: Parser String
positivenumber = digit >>>= \env d ->
(
positivenumber >>>= \env n ->
parserReturn env ([d] ++ n)
)
+++
parserReturn env [d]
-- Integer number or variable
-- number ::= <positivenumber> | <variable>
number :: Parser String
number = positivenumber +++
(
variable >>>= \env v ->
parserReturn env (bind env v) -- in case of var we have to bind wrt the only syuntax check
) -- substitutes the variables with their values
-- Arithmetic positive factor made of integer numbers or arithmetic expression inside parentheses
-- apositivefactor ::= <number> | ( <aexp> )
apositivefactor :: Parser Int
apositivefactor = (
number >>>= \env n ->
parserReturn env (read n :: Int ) -- Different from the only syntax parsing: we have to cast the string and memorize in the env the value (int)
)
+++
(
char '(' >>>= \env _ ->
aexpr >>>= \env e ->
char ')' >>>= \env _ ->
parserReturn env e
)
-- Arithmetic negative factor made by negating positivefactor
-- anegativefactor ::= - | <apositivefactor>
anegativefactor :: Parser Int
anegativefactor = char '-' >>>= \env _ ->
apositivefactor >>>= \env f ->
parserReturn env (f * (-1)) -- Different, but just to reverse sign
-- Arithmetic can be negative or positive factor
-- afactor ::= <apositivefactor> | <anegativefactor>
afactor :: Parser Int
afactor = anegativefactor +++ apositivefactor
-- Evaluation of the aexpr wich contains * or /
-- aterm ::= <afactor> | <afactor> <aexpOp2> <aterm>
aterm :: Parser Int
aterm = afactor >>>= \env f ->
(
char '*' >>>= \env _ ->
aterm >>>= \env t ->
parserReturn env (f * t) -- here operands can be applied because the values have been sobstituted by the casting in the previous defined functions
)
+++
(
char '/' >>>= \env _ ->
aterm >>>= \env t ->
parserReturn env (fromIntegral (div f t)) -- fromintegral converts from integer to int
)
+++
parserReturn env f
-- Evaluation of arithmetic expr
-- aexpr ::= <aterm> | <aterm> <aexpOp1> <aexp>
aexpr :: Parser Int
aexpr = aterm >>>= \env t ->
(
char '+' >>>= \env _ ->
aexpr >>>= \env e ->
parserReturn env (t + e)
)
+++
(
char '-' >>>= \env _ ->
aexpr >>>= \env e ->
parserReturn env (t - e)
)
+++
parserReturn env t
-- BOOLEAN EXPRESSIONS
-- evaluation of Boolean factor made of Arithmetic expression combined by comparison operator
-- bfactor ::= <aexp> | <aexp> <comparisonOp> <aexp> | <variable>
bfactor :: Parser Bool
bfactor = (aexpr >>>= \env a1 ->
(
char '<' >>>= \env _ ->
aexpr >>>= \env a2 ->
parserReturn env (a1 < a2)
)
+++
(
char '>' >>>= \env _ ->
aexpr >>>= \env a2 ->
parserReturn env (a1 > a2)
)
+++
(
char '=' >>>= \env _ ->
aexpr >>>= \env a3 ->
parserReturn env (a1 == a3)
)
+++
(
char '<' >>>= \env _ ->
char '=' >>>= \env _ ->
aexpr >>>= \env a2 ->
parserReturn env (a1 <= a2)
)
+++
(
char '>' >>>= \env _ ->
char '=' >>>= \env _ ->
aexpr >>>= \env a2 ->
parserReturn env (a1 >= a2)
)
+++
(
char '!' >>>= \env _ ->
char '=' >>>= \env _ ->
aexpr >>>= \env a2 ->
parserReturn env (a1 >= a2)
)
)
+++
(
variable >>>= \env v ->
if ((bind env v) == "True") || ((bind env v) == "False")
then
parserReturn env (read (bind env v) :: Bool) -- To avoid a type missmatch substitutes the variables with their values and cast string in boolean
else
failure
)
-- Evaluation of bterm
-- bterm ::= <bfactor> | ( <bexp> ) | ! <bexp>
bterm :: Parser Bool
bterm =
((trueKeyword +++ falseKeyword) >>>= \env b1 -> parserReturn env (read b1 :: Bool)) +++
(bfactor >>>= \env b2 -> parserReturn env b2) +++
(char '(' >>>= \env _ -> bexpr >>>= \env b3 -> char ')' >>>= \env _ -> parserReturn env b3) +++
(char '!' >>>= \env _ -> bexpr >>>= \env b4 -> parserReturn env (not b4))
-- Evaluation of bexpr
-- bexp ::= <bterm> | <bterm> <bexpOp> <bexp>
bexpr :: Parser Bool
bexpr = bterm >>>= \env b1 ->
(
char '&' >>>= \env _ ->
bexpr >>>= \env b2 ->
parserReturn env (b1 && b2)
)
+++
(
char '|' >>>= \env _ ->
bexpr >>>= \env b2 ->
parserReturn env (b1 || b2)
)
+++
parserReturn env b1
-- COMMAND EXPRESSIONS
-- Skip command is composed of skip keyword and semicolon
-- skipcommand ::= skip <semicolon>
skipCommand :: Parser String
skipCommand = skipKeyword >>>= \env sk ->
semicolon >>>= \_ s ->
parserReturn env (s ++ sk)
-- This function recognizes the assignment command, in particular the variable
-- and the assigned value (integer or Boolean), and also the assigment to an element of an array.
-- assignmentcommand ::= <variable> := (<aexp> | <bexp>) <semicolon> | <letter> := { <array> } <semicolon>
assignmentCommand :: Parser String
assignmentCommand = (variable >>>= \env v ->
char ':' >>>= \env _ ->
char '=' >>>= \env _ ->
(
bexpr >>>= \env b ->
semicolon >>>= \env s ->
parserReturn (setEnv v (show b) env) (v ++ ":=" ++ (show b) ++ s)
)
+++
(
aexpr >>>= \env a ->
semicolon >>>= \env s ->
parserReturn (setEnv v (show a) env) (v ++ ":=" ++ (show a) ++ s)
))
+++
(sat isLetter >>>= \env v ->
char ':' >>>= \env _ ->
char '=' >>>= \env _ ->
char '{' >>>= \env op ->
arrayType >>>= \env ar -> --this read the array elements, so it parse a list of integer
char '}' >>>= \env cp ->
semicolon >>>= \env s ->
parserReturn (saveArray env [v] ar ) ([v] ++ ":=" ++ [op] ++ (show ar) ++ [cp] ++ s) -- in order to save the array, manipulate env with savearray
)
-- The functions for saving arrays are arrayType and saveArray. The first, arrayType returns an [int] list
-- from the parsing of the elements, taken as a parameter by savearray with the env and the variable,
-- to save the single elements in the env, i.e. y:={2,5}; -> y[0]:=2; y[1]:=5;
-- array ::= <afactor> | <afactor> <colon> <array>
arrayType :: Parser [Int]
arrayType = afactor >>>= \env n ->
(
colon >>>= \env c ->
arrayType >>>= \env f ->
parserReturn env ([n] ++ f)
)
+++
parserReturn env [n]
saveArray :: Env -> String -> [Int] -> Env
--foldl :: (a -> b -> a) -> a -> [b] -> a
saveArray env var list = foldl (\e v -> setEnv (fst v) (snd v) e) env l -- in the v = [(name, value)]
-- zipWith:: (a -> b -> c) -> [a] -> [b] -> [c] makes a list, its elements are calculated from the function and the elements of input lists occuring at the same position in both lists
where l = zipWith (\val index -> -- so this we are going to memorize in the env in form of string
(var ++ "[" ++ (show index) ++ "]", show (val) )) list [0..] -- So the list in out is a string of this pattern
-- For the For statement, LIMPid first evaluates the value of the variable that represents the number of iterations of the program that will be execute,
-- then parses the program (parseprogram) without its evaluation and computes the function repeatNTimes
-- forcommand ::= for <space> <variable> <space> times <space> { <space> <program> <space> }
forCommand :: Parser String
forCommand = forKeyword >>>= \env f ->
variable >>>= \env v ->
timesKeyword >>>= \env t ->
openPargraf >>>= \env op ->
parseprogram >>>= \env p ->
repeatNTimes env p v >>>= \env r ->
closePargraf >>>= \env cp ->
semicolon >>>= \env s ->
parserReturn env (f ++ v ++ t ++ op ++ r ++ cp ++ s)
-- RepeatNTimes takes as parameters the env with the variable for the iteration evaluated
-- and the program parsed but not executed.
-- So, if there are not iteration to be executed (the variable is zero or a negative number),
-- then LIMPid leaves the program only parsed and not evaluated.
repeatNTimes :: Env -> String -> String -> Parser String
repeatNTimes env p v = if bind env v <= "0" then -- Condition is evaluated at each iteration of the for statement
parserReturn env p
else
parserReturn env (v ++ ":=" ++ v ++ "-" ++ "1" ++ ";") >>>= \env dec-> -- Is like we read in the code this statement
parserReturn (getEnv (parse program env dec)) dec >>>= \envdec _ -> -- And we use it to update the env with such a statement
parserReturn (getEnv (parse program envdec p)) p >>>= \envf _ ->
repeatNTimes envf p v -- executes again the for with the new environment in a recursively way
-- If command
-- ifcommand ::= if <space> ( <bexp> ) <space> then { <space> (<program> | <program> else { <space> <program>) } <semicolon>
ifCommand :: Parser String
ifCommand = ifKeyword >>>= \env i ->
openPar >>>= \env op ->
bexpr >>>= \env b ->
closePar >>>= \env cp ->
openPargraf >>>= \env t ->
if b
then
program >>>= \envTrue p1 ->
(
elseKeyword >>>= \env e ->
parseprogram >>>= \env p2 ->
closePargraf >>>= \env ei ->
semicolon >>>= \env s ->
parserReturn envTrue (i ++ op ++ (show b) ++ cp ++ t ++ p1 ++ e ++ p2 ++ ei ++ s)
)
+++ --whithout else branch
(
closePargraf >>>= \env ei ->
semicolon >>>= \env s ->
parserReturn envTrue (i ++ op ++ (show b) ++ cp ++ t ++ p1 ++ ei ++ s)
)
else
parseprogram >>>= \env p1 ->
(
elseKeyword >>>= \env e ->
program >>>= \envFalse p2 ->
closePargraf >>>= \env ei ->
semicolon >>>= \env s ->
parserReturn envFalse (i ++ op ++ (show b) ++ cp ++ t ++ p1 ++ e ++ p2 ++ ei ++ s)
)
+++
(
closePargraf >>>= \env ei ->
semicolon >>>= \env s ->
parserReturn env (i ++ op ++ (show b) ++ cp ++ t ++ p1 ++ ei ++ s)
)
-- While command
-- whilecommand ::= while <space> ( <bexp> ) <space> { <space> do <space> <program> <space> } <semicolon>
whileCommand :: Parser String
whileCommand = whileKeyword >>>= \env w ->
openPar >>>= \env op ->
parsebexpr >>>= \env b ->
closePar >>>= \env cp ->
openPargraf >>>= \env ogr ->
doKeyword >>>= \env t1 ->
parseprogram >>>= \env p ->
closePargraf >>>= \env cgr ->
semicolon >>>= \env s ->
if (getCode (parse bexpr env b)) -- the bexpr is re-evaluated every cicle
then
parserReturn (getEnv (parse program env p)) p >>>= \envw _ -> -- execution of the p program inside the while
parserReturn (getEnv (parse program envw (w ++ op ++ b ++ cp ++ ogr ++ t1 ++ p ++ cgr ++ s))) (w ++ op ++ b ++ cp ++ ogr ++ t1 ++ p ++ cgr ++ s) -- re-execution of the same commands
else
parserReturn env (w ++ op ++ b ++ cp ++ ogr ++ t1 ++ p ++ cgr ++ s)
-- Do While command parserReturn env (d ++ opg ++ p ++ cpg ++ op ++ b ++ cp ++ s)
-- dowhilecommand ::= do <space> { <space> do <space> <program> <space> } while <space> ( <bexp> ) <space> <semicolon>
dowhileCommand :: Parser String
dowhileCommand = doKeyword >>>= \env d ->
openPargraf >>>= \env opg ->
parseprogram >>>= \env p ->
closePargraf >>>= \env cpg ->
whileKeyword >>>= \env w ->
openPar >>>= \env op ->
parsebexpr >>>= \env b ->
closePar >>>= \env cp ->
semicolon >>>= \env s ->
parserReturn (getEnv (parse program env p)) p >>>= \envw _ -> -- execution of the p program inside the do - block for the first iteration
if (getCode (parse bexpr env b)) -- the bexpr is re-evaluated every cicle
then -- program reexcuted with the new env and the execution of the code
parserReturn (getEnv (parse program envw (d ++ opg ++ p ++ cpg ++ w ++ op ++ b ++ cp ++ s))) (d ++ opg ++ p ++ cpg ++ w ++ op ++ b ++ cp ++ s)
else
parserReturn env (d ++ opg ++ p ++ cpg ++ w ++ op ++ b ++ cp ++ s)
-- Command can be skip, assignment, if, while, for, arithmetic expression or boolean expression
command :: Parser String
command = (skipCommand +++ assignmentCommand +++ ifCommand +++ whileCommand +++ forCommand +++ dowhileCommand) >>>= \env c ->
parserReturn env c
-- Program is a set of command or a single command
program :: Parser String
program = command >>>= \env c -> ( program >>>= \env p -> parserReturn env (c ++ p)) +++ parserReturn env c
-- +++++++++++++++++++++++++++ INTERACTIVE SHELL +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
parser :: String -> IO String
parser xs =
do
putStr "LIMPid#>"
hFlush stdout -- flushes all the buffered output data
ys <- getLine
case ys of
":printmem" ->
do
-- here code parsing and memory situation
putStrLn ""
putStrLn "-+-+ Parsed Code +-+-"
if xs == [] then
putStrLn ""
else
putStrLn (getCode (parse parseprogram [] xs)) -- here code parsing
putStrLn ""
putStrLn "-+-+ Memory +-+-"
putStrLn (getMemory (parse program [] xs)) -- like a tostring to see the mem situation, here the real execution of the program
putStrLn ""
parser xs
":syntax" ->
do
-- here output the formal grammar
putStrLn "-+-+ LIMPid Syntax +-+-"
putStrLn ""
putStrLn " program := <command> | <command> <program>"
putStrLn " command ::= <skipcommand> | <assignmentcommand> | <ifcommand> | <whilecommand>"
putStrLn " skipcommand ::= skip <semicolon>"
putStrLn " assignmentcommand ::= <variable> := (<aexp> | <bexp>) <semicolon> | <letter> := { <array> } <semicolon> "
putStrLn " array ::= <afactor> | <afactor> <colon> <array> "
putStrLn " ifcommand ::= if <space> ( <bexp> ) <space> { <space> (<program> | <program> else <space> <program>) } <semicolon>"
putStrLn " whilecommand ::= while <space> ( <bexp> ) <space> { <space> do <space> <program> <space> } <semicolon>"
putStrLn " dowhilecommand ::= do <space> { <space> do <space> <program> <space> } while <space> ( <bexp> ) <space> <semicolon>"
putStrLn " forcommand ::= for <space> <variable> <space> times <space> { <space> <program> <space> } "
putStrLn " bexp ::= <bterm> | <bterm> <bexpOp> <bexp>"
putStrLn " bterm ::= <bfactor> | ( <bexp> ) | ! <bexp>"
putStrLn " bfactor ::= <aexp> | <aexp> <comparisonOp> <aexp> | <variable>"
putStrLn " aexpr ::= <aterm> | <aterm> <aexpOp1> <aexp>"
putStrLn " aterm ::= <afactor> | <afactor> <aexpOp2> <aterm>"
putStrLn " afactor ::= <apositivefactor> | <anegativefactor>"
putStrLn " anegativefactor ::= - | <apositivefactor>"
putStrLn " apositivefactor ::= <number> | ( <aexp> )"
putStrLn " number ::= <positivenumber> | <variable>"
putStrLn " positivenumber ::= <digit> | <digit> <positivenumber>"
putStrLn " variable ::= <letter> | <letter> <variabile>"
putStrLn " semicolon ::= ; | ; <space>"
putStrLn " digit ::= 0-9"
putStrLn " aexpOp1 ::= + | -"
putStrLn " aexpOp2 ::= * | /"
putStrLn " bexpOp ::= & | |"
putStrLn " comparisonOp ::= < | > | = | <= | >= | !="
putStrLn " letter ::= a-z"
putStrLn " space ::= \" \" "
parser (xs)
":help" ->
do
-- here the Help section whith the explanations of the possible commands
putStrLn "-+-+ LIMPid Help +-+-"
putStrLn ""
putStrLn " :printmem prints the parsed code and the status of the memory"
putStrLn ""
putStrLn " :syntax prints the LIMPid formal grammar"
putStrLn ""
putStrLn " :help prints the help with the commands of the program"
putStrLn ""
putStrLn " :quit stops the LIMPid program"
putStrLn ""
parser xs
":quit" ->
do
-- quit from the interpeter's shell
return []
otherwise ->
-- Error situation (input in the shell is not a valid command) JUST SYNTAX CHECK
case parse parseprogram [] ys of
[] ->
do
putStrLn "Syntax error! Please type \":help\""
parser xs
otherwise -> parser (xs ++ ys)
-- Call this functions to start the program (the Interpreter)
limpid :: IO String
limpid = do
putStrLn ""
putStrLn ""
putStrLn ""
putStrLn ""
putStrLn "-+-+-+-+-+- LIMPid Language Interpreter -+-+-+-+-+-"
putStrLn ""
putStrLn "Type \":help\" for commands"
putStrLn ""
putStrLn ""
parser []