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[ITMO] T05 Khamitsevich Alexey #1881

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107 changes: 79 additions & 28 deletions src/Expr.lama
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Original file line number Diff line number Diff line change
@@ -1,34 +1,29 @@
-- Expression evaluator

import List;
import State;
import World;

-- As association map which maps "\otimes" into "\oplus"
var ops = {
["+" , infix + ],
["-" , infix - ],
["*" , infix * ],
["/" , infix / ],
["%" , infix % ],
["==", infix ==],
["!=", infix !=],
["<" , infix < ],
["<=", infix <=],
[">" , infix > ],
[">=", infix >=],
["&&", infix &&],
["!!", infix !!]
};

var ops = {["+", infix +],
["-", infix -],
["*", infix *],
["/", infix /],
["%", infix %],
["==", infix ==],
["!=", infix !=],
["<", infix <],
["<=", infix <=],
[">", infix >],
[">=", infix >=],
["&&", infix &&],
["!!", infix !!]};
-- The evaluator for infix operators: takes an operator as a string
-- and two operand values, and returns the result
public fun evalOp (op, l, r) {
case assoc (ops, op) of
Some (f) -> f (l, r)
esac
case assoc(ops, op) of
Some(f) -> f(l, r)
esac
}

-- Evaluates an expression "expr" in a configuration "c".
-- A configuration is a pair of a state "s" and a world "w".
-- Returns a final configuration (if any)
Expand All @@ -48,7 +43,6 @@ public fun evalOp (op, l, r) {
-- Const (int) |
-- Binop (string, expr, expr) |
-- Ignore (expr)

-- Evaluates a list of expressions, properly threading a configurations.
-- Returns the final configuration and the list of values
fun evalList (c, exprs) {
Expand All @@ -63,14 +57,71 @@ fun evalList (c, exprs) {
esac
}

-- s <- [name,val] -- add
-- s(x) -- get
fun eval (c@[s, w], expr) {
failure ("evalExpr not implemented\n")
case expr of
Var(v) -> [c, s(v)]
| Skip -> [c, 0]
| Binop(op, expr1, expr2) ->
case evalList(c, {expr1, expr2}) of
[c, {left, right}] -> [c, evalOp(op, left, right)]
esac
| Const(i) -> [c, i]
| Assn(expr1, expr2) ->
case evalList(c, {expr1, expr2}) of
[c@[s, w], {Ref(left), right}] -> [[s <- [left, right], w], right]
esac| Seq(expr1, expr2) -> let [c, v] = eval(c, expr1) in eval(c, expr2)
| Read(v) ->
case readWorld(w) of
[r, w] -> [[s <- [v, r], w], 0]
esac
| Write(exp) ->
case eval(c, exp) of
[c@[s, w], new] -> [[s, writeWorld(new, w)], 0]
esac
| If(state, try, fls) ->
case eval(c, state) of
[c, v] -> if v then eval(c, try) else eval(c, fls) fi
esac
| While(state, body) ->
case eval(c, state) of
[c, 0] -> [c, 0]
| [c, _] -> let [c, _] = eval(c, body) in eval(c, While(state, body))
esac
| DoWhile(state, body) -> eval(c, Seq(body, While(state, body)))
| Ignore(body) -> [eval(c, body)[0], 0]
| Ref(vall) -> [c, Ref(vall)]
| _ -> [c, 0]
esac
}


-- expr = Var (string) |
-- Const (int) |
-- Binop (string, expr, expr)
-- Evaluates a program with a given input and returns an output
public fun evalExpr (input, expr) {
case eval ([emptyState, createWorld (input)], expr) of
[c, _] -> c.snd.getOutput
esac
case eval([emptyState, createWorld(input)], expr) of
[c, _] -> c.snd.getOutput
| Var(v) -> input(v)
| Const(i) -> i
| Binop(op, expr1, expr2) -> evalBinop(op, evalExpr(input, expr1), evalExpr(input, expr2))
esac
}

public fun evalBinop(op, expr1, expr2) {
case op of
"+" -> expr1 + expr2
| "-" -> expr1 - expr2
| "*" -> expr1 * expr2
| "/" -> expr1 / expr2
| "%" -> expr1 % expr2
| "<" -> expr1 < expr2
| ">" -> expr1 > expr2
| "<=" -> expr1 <= expr2
| ">=" -> expr1 >= expr2
| "==" -> expr1 == expr2
| "!=" -> expr1 != expr2
| "&&" -> expr1 && expr2
| "!!" -> expr1 !! expr2
esac
}
111 changes: 60 additions & 51 deletions src/Parser.lama
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
-- Parser

import Ostap;
import Lexer;
import List;
Expand All @@ -10,73 +9,83 @@ import Collection;

-- Signals an error; takes an error message and location info
fun error (msg, loc) {
failure ("%s at %d:%d\n", msg, loc.fst, loc.snd)
failure("%s at %d:%d\n", msg, loc.fst, loc.snd)
}

-- An attribute-processing functions
-- Attributes are:
-- Val --- a plain value (aka "rvalue")
-- Ref --- a reference to a mutable cell (aka "lvalue")
-- Void --- no value (aka "void"/"unit")

-- Checks if a plain value "val" can be used in the context described by
-- the attribute "atr".
fun assertValue (atr, v, loc) {
case atr of
Ref -> error ("reference expected", loc)
| Void -> Ignore (v)
| _ -> v
esac
case atr of
Ref -> error("reference expected", loc)
| Void -> Ignore(v)
| _ -> v
esac
}

fun assertVoid (atr, v, loc) {
case atr of
Void -> v
| Val -> error ("value expected", loc)
| _ -> error ("reference expected", loc)
esac
case atr of
Void -> v
| Val -> error("value expected", loc)
| _ -> error("reference expected", loc)
esac
}

-- A parser of "something" in brackets; l, r are left and right
-- brackets as parsers, p --- a parser of "something"
fun inbr (l, p, r) {
syntax (-l p -r)
syntax (-l p -r)
}

fun binop (op) {
[syntax (pos -s[op]), fun (l, loc, r) {
fun (a) {
assertValue (a, Binop (op, l (Val), r (Val)), loc)
}
}
]
[syntax (pos -s[op]), fun (l, loc, r) {fun (a) {assertValue(a, Binop(op, l(Val), r(Val)), loc)}}]
}

var primary = memo $ eta syntax (
-- decimal constant
loc=pos x=decimal {fun (a) {assertValue (a, Const (stringInt (x)), loc)}} |

-- identifier
x=lident {fun (a) {
case a of
Ref -> Ref (x)
| Void -> Ignore (Var (x))
| _ -> Var (x)
esac
}} |
$(failure ("the rest of primary parsing in not implemented\n"))),
basic = memo $ eta (expr ({[Right, {[s (":="),
fun (l, loc, r) {
fun (a) {assertValue (a, Assn (l (Ref), r (Val)), loc)}
}]}],
[Left , map (binop, {"!!"})],
[Left , map (binop, {"&&"})],
[Nona , map (binop, {"==", "!=", "<", ">", "<=", ">="})],
[Left , map (binop, {"+", "-"})],
[Left , map (binop, {"*", "/", "%"})]
},
primary)),
exp = memo $ eta syntax (basic | s1=basic s[";"] s2=exp {fun (a) {Seq (s1 (Void), s2 (a))}});

var primary = memo $ eta syntax (
-- decimal constant
loc=pos x=decimal {fun (a) {assertValue(a, Const(stringInt(x)), loc)}} |

-- identifier
x=lident {
fun (a) {
case a of
Ref -> Ref(x)
| Void -> Ignore(Var(x))
| _ -> Var(x)
esac
}
} |
inbr[s("("), exp, s(")")] |

kRead expres=inbr[s("("), lident, s(")")] {fun (a) {assertVoid(a, Read(expres), loc)}} |
kSkip {fun (a) {assertVoid(a, Skip, loc)}} |
kWrite expres=inbr[s("("), exp, s(")")] {fun (a) {assertVoid(a, Write(expres(Val)), loc)}} |
kIf expres=exp kThen s1=exp s2=ifRec {fun (a) {If(expres(Val), s1(a), s2(a))}} |
kThen {fun (a) {assertVoid(a, Skip, loc)}} |
kWhile expres=exp kDo s=exp kOd {fun (a) {assertVoid(a, While(expres(Val), s(Void)), loc)}} |
kDo s=exp kWhile expres=exp kOd {fun (a) {assertVoid(a, DoWhile(expres(Val), s(Void)), loc)}} |
kFor i0=exp s[","] cond=exp s[","] step=exp kDo body=exp kOd {
fun (a) {assertVoid(a, Seq(i0(Void), While(cond(Val), Seq(body(Void), step(Void)))), loc)}
}
),
basic = memo $ eta (
expr({[Right, {[s(":="), fun (l, loc, r) {fun (a) {assertValue(a, Assn(l(Ref), r(Val)), loc)}}]}],
[Left, map(binop, {"!!"})],
[Left, map(binop, {"&&"})],
[Nona, map(binop, {"==", "!=", "<", ">", "<=", ">="})],
[Left, map(binop, {"+", "-"})],
[Left, map(binop, {"*", "/", "%"})]}, primary)
),
exp = memo $ eta syntax (
basic |
s1=basic s[";"] s2=exp {fun (a) {Seq(s1(Void), s2(a))}}
),
ifRec = memo $ eta syntax (
kElif expres=exp kThen try=exp fls=ifRec {fun (a) {If(expres(Val), try(a), fls(a))}} |

kElse s2=exp kFi {fun (a) {s2(a)}} |

kFi {fun (a) {assertVoid(a, Skip, loc)}}
);
-- Public top-level parser
public parse = syntax (s=exp {s (Void)});
public parse = syntax (s=exp {s(Void)});
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