Some invalid behavior with 9 ... 1531

[zaLTys]

Hi @FeynmanFan

First of all - amazing course and great exercise files!

So at random tried changing the test to evaluate that 9 is not a prime and that 1531 is a prime, faced this error:

I am not sure what causes this issue, probably i assignment to 3 but I could not put my finger on it, what am I missing?

[zaLTys]

var modBlock = Expression.Block(
    new[] { i, boundary },
    Expression.IfThen(
        Expression.Equal(Expression.Modulo(value, i), Expression.Constant(0)),
        Expression.Return(returnLabel, Expression.Constant(false))
    ),
    Expression.AddAssign(i, Expression.Constant(2))
);

In this block, it first checks if value is divisible by i, and if so, it immediately returns false (indicating that value is not prime). Afterwards, it increments i by 2.

The problem is that this block gets compiled as a separate unit and does not carry the scope of i and boundary outside. When i is incremented here, it does not affect the i in the outer scope (the i used in the loop condition). This might be the reason we are getting a division by zero error.

Potential fix:

Expression modBlock = Expression.IfThen(
    Expression.Equal(Expression.Modulo(value, i), Expression.Constant(0)),
    Expression.Return(returnLabel, Expression.Constant(false))
);

Expression incrementI = Expression.AddAssign(i, Expression.Constant(2));

and then

Expression.Loop(
    Expression.IfThenElse
    (
        Expression.LessThanOrEqual(i, boundary),
        Expression.Block(modBlock, incrementI),
        Expression.Break(label)
    ),
    label
)

[FeynmanFan]

I think your analysis is correct. Submit a pull request and we'll get your name on the fix :). CBB

…

On Tue, Jun 27, 2023, 6:26 AM zaLTys ***@***.***> wrote: var modBlock = Expression.Block( new[] { i, boundary }, Expression.IfThen( Expression.Equal(Expression.Modulo(value, i), Expression.Constant(0)), Expression.Return(returnLabel, Expression.Constant(false)) ), Expression.AddAssign(i, Expression.Constant(2)) ); In this block, it first checks if value is divisible by i, and if so, it immediately returns false (indicating that value is not prime). Afterwards, it increments i by 2. The problem is that this block gets compiled as a separate unit and does not carry the scope of i and boundary outside. When i is incremented here, it does not affect the i in the outer scope (the i used in the loop condition). This might be the reason we are getting a division by zero error. Potential fix: Expression modBlock = Expression.IfThen( Expression.Equal(Expression.Modulo(value, i), Expression.Constant(0)), Expression.Return(returnLabel, Expression.Constant(false)) ); Expression incrementI = Expression.AddAssign(i, Expression.Constant(2)); and then Expression.Loop( Expression.IfThenElse ( Expression.LessThanOrEqual(i, boundary), Expression.Block(modBlock, incrementI), Expression.Break(label) ), label ) — Reply to this email directly, view it on GitHub <#1 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAIFVJGYOIGJPFCGR64BYYTXNK7N7ANCNFSM6AAAAAAZVHHP5Q> . You are receiving this because you were mentioned.Message ID: ***@***.***>