Support for prefix operators about effekt HOT 5 OPEN

Minor nitpick: We might want to call them prefixNeg and prefixNot...

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-(x + y) is perfectly valid and very commonly used mathematically expression. I have never seen someone write 0 - (x + y) instead. Do you have an example where this appears as a code smell?

For example, the normal distribution is defined as N(x; mu, sigma) ~ e^(-((mu - sigma)^2 / (2 * sigma^2)). I have never seen it given as N(x; mu, sigma) ~ e^(0 - ((mu - sigma)^2 / (2 * sigma^2)) instead. If someone wanted to implement this in Effekt, I would imagine the normal user would like to stick as close as possible to common mathematical notations and not having to think about how to desugar it.

Edit: A perhaps easier example: negative fractions. It is more convenient and more common to write - (1 / 2) instead of 0 - (1 / 2).

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Yes, right. That's a typo... edited

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Why would we want to write -(1+2)? For prefixNot I can understand it, but -(1+2) is a smell in my opinion. Is there a usecase where you think this is better than 0 - (1 + 2)?

Another prefix operator that could be useful is bitwise negation ~x where typically we wouldn't desugar it into "subtraction".

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Ok, here are two points to address

1. spaces: a lot of Effekt code is written by students (in theses, etc.). Since we do not have a nice formatter, they end up using the most creative way to use whitespaces. I would be very happy if 1-x would just fail and force them to write 1 - x. Ideally, also 1- x should fail.

2. - as unary operator. This is mostly personal taste. I have a dislike for prefix and postfix operators. I almost always write x = x + 1 instead of x++. I am also happy to write 0 - x instead of x, like here:

Actually, I typically write -1 * ... instead of 0 - ...and I think it works pretty well in your example as well.

The normal distribution is a bit of a red hering, since you use other operators that typically also don't exist in PLs (like ^ for exponentiation).

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