Interpreter in Smalla

Interp.smalla

/* 8*7 */
val input1: {l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int} =
    {l:8, op:inj[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit](Times:()), r:-7}
in
/* 0>10 */
val input2: {l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int} =
    {l:0, op:inj[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit](Gt:()), r:10}
in
/* 10+10 */
val input3: {l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int} =
    {l:10, op:inj[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit](Plus:()), r:10}
in
/* 10==10 */
val input4: {l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int} =
    {l:10, op:inj[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit](Eq:()), r:10}
in
/* 1<10 */
val input5: {l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int} =
    {l:1, op:inj[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit](Lt:()), r:10}
in
/* !1 */
val input6: {l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int} =
    {l:0, op:inj[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit](Not:()), r:1}
in
/* 0 && 1 */
val input7: {l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int} =
    {l:0, op:inj[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit](And:()), r:1}
in
/* 0 || 1 */
val input8: {l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int} =
    {l:0, op:inj[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit](Or:()), r:1}
in
/* Converts an Int to Boolean */
def itob(i:Int):Boolean = if (i==0) false else true
in
/* Recrusively multiplies two positive numbers */
def mult(l:Int):Int=>Int=>Int =
    (r:Int)=>(a:Int)=>
        if (r<1)
            a
        else
            mult(l)(r-1)(l+a)
in
/* Wrapper for mult. Accepts negative or positive */
def multiply(l:Int):Int=>Int =
    (r:Int)=>
        if ((l<0) && (r<0)){
            mult(-l)(-r)(0)
        }else{
            if (l<0){
                -mult(-l)(r)(0)
            }else{
                if (r<0){
                    -mult(l)(-r)(0)
                }else{
                    mult(l)(r)(0)
                }
            }
        }
in
def eval(e:{l:Int, op:[Plus:Unit, Minus:Unit, Times:Unit, Eq:Unit, Lt:Unit, Gt:Unit, Not:Unit, And:Unit, Or:Unit], r:Int}):[I:Int, B:Boolean, U:Unit] = e.op match[[I:Int, B:Boolean, U:Unit]] {
    case Plus:nil => inj[I:Int, B:Boolean, U:Unit](I: (e.l+e.r))
    case Minus:nil => inj[I:Int, B:Boolean, U:Unit](I: (e.l-e.r))
    case Times:nil => inj[I:Int, B:Boolean, U:Unit](I: multiply(e.l)(e.r))
    case Eq:nil => inj[I:Int, B:Boolean, U:Unit](B: (e.l==e.r))
    case Lt:nil => inj[I:Int, B:Boolean, U:Unit](B: (e.l<e.r))
    case Gt:nil => inj[I:Int, B:Boolean, U:Unit](B: (e.r<e.l))
    case Not:nil => inj[I:Int, B:Boolean, U:Unit](B: (!itob(e.r)))
    case And:nil => inj[I:Int, B:Boolean, U:Unit](B: (itob(e.l) && itob(e.r)))
    case Or:nil => inj[I:Int, B:Boolean, U:Unit](B: (itob(e.r) || itob(e.l)))
}
in
/* Print the union type returned by eval */
def printVal(v:[I:Int, B:Boolean, U:Unit]):Unit = v match[Unit] {
    case I:i => print(i)
    case B:b => print(b)
    case U:u => print(u)
}
in
/* Run tests */
{
    printVal(eval(input1));
    printVal(eval(input2));
    printVal(eval(input3));
    printVal(eval(input4));
    printVal(eval(input5));
    printVal(eval(input6));
    printVal(eval(input7));
    printVal(eval(input8))
}

/**************
Expected output:
-56
false
20
true
true
false
false
true

Value:
  ()
***************/