Parsim is a monadic parser for a simple imperative language.
Implemented to study {functors, applicatives, monads}.
<expr> ::= <expr> <op> <expr> | <symbol> | <value>
<symbol> ::= [a-zA-Z]+
<value> ::= [1-9][0-9]* | 0
<op> ::= + | - | * | == | <
<prog> ::= <symbol> = <expr>;
| <prog> <prog>
| if (<expr>) then {<prog>} else {<prog>}
| while (<expr>) {<prog>}
| return <expr>;
The corresponding ADT is defined in Types.hs.
Currently supporting only integer values (Int type).
Given the following program (defined in testdata/raw/test1-10.in):
y = 1 * 2;
x = 4 + y;
if (y == 2) then {
z = 0;
while (z < 3) {
x = x + 1;
y = x + 2;
z = z + 1;
}
return y;
} else {
return x + y;
}
you can use make run INPUT=testdata/raw/test1-10.in to run it, obtaining the following output:
P (Right 11)
which indicates a successful run.
You can also write an immediate short program, like this:
make run INPUT=<(echo "x = 23; y = x - 17; return x * y;")
Output: P (Right 138).
E.g. missing ;
a = 15;
b = 25;
while (0 < b) {
if (b < a) then {
a = a - b
} else {
b = b - a;
}
}
c = a;
return c;
Output:
P (Left "Syntax error")
Variable x is uninitialized:
z = 0;
while (z < 3) {
x = x + z;
z = z + 1;
}
return z;
Output:
P (Left "Uninitialized variable")
No return path:
x = 10;
y = 20;
z = x + y;
Output:
P (Left "Missing return")